I have a 1969 Firebird convertible getting painted right now. New interior gets put in when that's done. Then its time to look at the engine. When I bought the car last year, it was a driver with a spare motor that had been pulled because it overheated at stop lights. After reading many posts, I'm leaning toward it having the wrong water pump or the spacer hadn't been "massaged" to fit better. The water pump has been changed. Either way, I have it on a stand and the car has another 350 in it that is a dog. In running the numbers, the one on the stand appears to be a 1969 350 HO with "48" heads. Different carb, distributer and water pump has been changed. I'm hopping it has not been touched internally. Plan is to pull it apart next fall and see what I have and what it needs.
Reason for this post is from what I have read, there are not too many of these around and this might be a chance to answer some questions and dispel some myths so if anyone has a question, or a comment on what to look for when pulling it down, feal free to post or send me a message.
Of all the Pontiac forums, this one seems to have some members that are really smart and know there stuff.
Not sure where I'm going with the distributer. One in it is not OEM, it's HEI and I have heard of clearance issues. Hell, I don't even know if it works. The other thing is the carb. Have read that I need one that is factory correct and I will be happy, but those are hard to find and lots of $$$ so we shall see.

Congrats on a '69 convertible. But even more if it is a true HO car. That is really rare. This chart shows the #48 heads as big valve 10.5 compression.Pontiac HeadsThere are many reasons for it to overheat so I would check the basics first.

Original is always best, but, you can use a different carb if it has the right jets and rods inside. I prefer a post 1973 Q-jet because I can convert it to electric choke. Look up your factory carb specs here> Carb specs

If you open the engine, check the cam out for sure. The Wallace Racing site has the cam codes too. And block codes.

I prefer the HEI distributor. No points maintenance, hotter spark. It is a tight fit against the firewall, nothing a small sledge won't correct. You can bench test it by clamping it in a vise and rigging it like it was in a car. Just watch out for the spark. It can reach a foot away and bite like a MF.

Thanks for the tips. Im just guessing water pump because it has been changed. First thing is to verify it has the proper one.
Car was not an HO car, but that was what was in it when the previous owner bought it about 20 years ago.
For a second I almost thought of building a "tribute" TA, but so much has been changed from stock, Im just going to make it what I want. I'm having the painter put on the HO stripes from 67,69. We will see how that goes. Interior is getting redone, just back to factory but it will be new.

I'm slowly getting the wife warmed up to the idea of doing the HO motor. Should hit the paint booth this week or next and I'm putting HO stripes on the side, so I kind of HAVE to put the HO in.
Not looking to build a race car, but I would like to just do a "to spec" HO 350.
I got to thinking, will I have any problem on pump gas with 10 to 1 compression? The gas we have now is way different.

Yes 10:1 will be tough. i have been down this road many times.
I would seek out better gasoline if you want to go that route with that compression.
You have to be on point with tuning but even then you cant set the timing to where it would be optimal for the engine to run like it should.
I would drop it down to 9:1 with custom pistons since there is really no choice with an off the shelf piston.

So what will it do if rebuilt to stock specs with the correct carb? Will I fight pinging and just have to retard the timing a bit? There for not getting everything out of an HO like they were made. Am I just looking at running a higher octane? It's not going to be a daily driver, but I want to take it on a couple of 200 to 300 mile trips and not have to worry about fuel.
So for that I'm thinking build it to run on pump gas.

You could try an octane additive or aviation gas if you have a small airport locally. The problem with retarding timing to compensate for the pinging is that it greatly effects engine performance and just adds heat to the exhaust so the engine will run hotter.
But you really need to figure out what the actual compression ratio is. you really need to know the exact CC of the combustion chambers of the heads, the piston the deck clearance, the volume of the valve re leafs in the pistons and the thickness of the head gasket.
some of these cylinder heads did not have the supposed combustion chamber size. Not all 72 cc heads had a 72 cc chamber.
If you have a set of the #48 350 HO heads, those chambers were supposedly 68cc chambers. But you never know.
Back many years ago when we had good gasoline we would run Sunoco 93 in these engines without any problems.

Thanks for the tips. Sounds like I'm going to have to really pick the brain of the engine builder and get his thought also. He got the shop from his dad and has a long time following from the Pontiac crowd. When I first approached him about the 350HO and explained that I just wanted to refresh it and keep it stock, he commented I could do that, but I would really have to watch my tune. Didn't ask for clarification at the time.
I got really excited when I was doing the research and found that I had a 350HO with #48 heads. Factory 325HP with no build, COOL.
Now I'm coming to the conclusion that I can't really run that engine on todays gas. Or I can, with a bunch of modifications. Hardened valve seats, Lower comp pistons, different cam. Then its not really a 350 HO then is it?
I got all summer to decide..........