After being tired of not being able to see the road, and the fact that the left low beam burned out, I purchased some Sylvania XTRAVision headlights for my 68 bird. After the normal hassle of trying to get the headlight back into the bucket, I went to connect the 3-prong socket to the light and it just barely slid on. The slightest touch and it fell off. I'm sure the first real bump I would hit on the road would have knocked it off. I finally figured out that the tabs on the new bulb do not extend out from the back of the bulb like the original T3 bulb. The T3 has moulded tits that extend out about 3/8" and the tabs are attached to the end of the tits. That 3/8" difference is what keeps the plug from securely fastening to the light. I could probably trim down the socket but that would be a last resort. Are there any halogen lights on the market that have the correct tabs?

I went through similar when I converted the headlights for driving on the left. I also wanted something brighter than the crappy sealed beam units that came on the car, so changed to separate reflectors with QH (H4 and H1) bulbs.

For the low/high beam (outside) lamps I ended up taking out each brass terminal in the 3prong socket and retensioning them and they seem to be holding ok.

I am not sure if you are changing your high beam (inside) units, but the H1 bulbs have only one pin, using the holder (which has a male pin on it) for the ground connection. I bought two-pin male sockets and single-pin female sockets (on ebay) and made an adapter with the bulb/holder end as flying leads. As you say the pins are shorter now and just hold... I use cable ties to hold the adapter cable in place and to keep the sockets from vibrating off.

I found the sockets on ebay were of variable quality and ended up buying a couple of batches of each and chose the best (ones that didn't drop off).

I got brighter lights by installing relays to power the lights. The original wire from the High/low switch turns the relays off/on and a heavy gauge wire from the main power buss supplies the power to the lights through the relays. Juice for the lights has to travel from the power up source through the firewall, to the headlight switch, to the High/low switch, back out the firewall junction block to the splitter and on to the headlight. Every solder, junction and switch can add a bit of resistance and cause a voltage drop. I was getting less than 10 volts at the lights, I now get 14+. The lights are vastly brighter with standard lamps. Good ground is needed as well.

I did the same thing as Bluebird with the relays and it does help.

But back to the original question,
I don't know that the bulb is your problem. I used some (Wagner) Halogen H5001 & H5006 sealed beams on my car without any problems at all. Though I don't remember them having the big rubber cup on the back and it was many years ago now that I did that (plus the car is in deep winter storage right now and I can't get to it to check.) But, make sure that terminals inside the plastic plug are in the plug all the way, and coming close to the front of the plug. As options you could pick up a new headlight connector pigtail and see if will fit better on your headlight and the wire it into your harness if it does. Or as a temp. fix pull the wires out of the pigtail put a male end on the other end of each wire and use them as short jumper wires.
Though the simpleist may be to just cut the front of the plug off.
Lee

I had the same problem with replacement headlights having the prongs be too short to fit the socket. I was replacing the light because the prongs had broken off the light. I re-soldered the prongs and used the old light.

I saw the relay system discussed in a car mag and it sounded like a great idea. It's good to hear some of you have done it and it works. The relay system probably has new sockets that fit modern headlights. I may do this in the near future. I have trouble seeing through the old windshield with dim lights with my 51 year old eyeballs.

Thanks for all the responses. I think Lee has the right idea, certainly the easiest, and trim the shroud off the plug. The high beam does not have a shroud, so it should be alright.
PS: I found that leaving the spring off the rims until the last thing and using a crochet needle to grab the spring and attach to the rim worked the best.