Hi all.
Yes, I think this is my 1st post. I have been using this site for a ton of useful information but have a question at this point that I can't find already answered.
Anyways, I have a '67 Firebird with original 326HO. Motor was running but on tear-down, noticed a few issues. Would need a total rebuild. With the money I am putting into it I figured a 400 would be the better choice. (With many recommendations from this board).
I have a source for a remanufactured 400, block number 988,577(?) and head number 4X, 6X or 5C. 2 3/4" cam centering ring. Specifies it is for a '73-'74 Pontiac XX.
or
400, I can request head casting number, 5 motor mounts on left, 4 on right. 2 1/2" cam centering ring. Specs for 75-79 Pontiac XX.
or
400, I take the heads they have at moment, specs for 67-69 Pontiac XX.
I would like to keep my existing '67 Timing housing, pulleys, A/C mounts and pulleys etc as all are either new or in very good condition.
My questions:
1. I am under the impression that the years are crossable as to the accessory equipment on the front of the motor, is this true and will I run into any issues using my existing equipment?
2. Which block era would be the best? (Wall thickness, etc.)
3. Heads - Would like to make sure I get the big valve stuff.
4. Motor mounts - Do the newer, multi mount blocks include the correct holes for the mount in the '67?
5. Transmission mounting - I believe all the above engines will have the correct mounting holes for the early Pontiac transmissions, just want to get this verified.

Thanks so much in advance for your valuable input. THis has been one hell of a project and am ready to drop the powerplant and trans in at this point.