I just bought a 401 Nail that came from the factory with a T400 behind it- not sure with the smaller Nails, but I b'leive you just bolt up the flexplate and tranny bolts right up to the engine-Might wanna get another opinion, tho.....
You need a flexplate from a 64-66 Nailhead, you can then enlarge the center hole to fit over you crank. Then you need a bushing from Carmen Faso 716.693.4090 - J&C's Parts 7127 Ward Road North Tonawanda, NY 14120 for the end of the crank... Then you need a ST400 or SP400 from a 64-66 Nailhead.... That'll pretty much do it.. Though these trannies can be found in other vehicles.... More info on where to find the trannies... "A source for TH400 trannys: wanted to give everyone a heads up on a good place to look for TH400 transmissions. keep an eye out for jeep pick-ups and wagoneers 1965 to 1972. they have the same bell housing as a 401 nailhead and are th400's. you can unbolt the transfer case adapter and bolt on a 4" tailhousing and your ready to go! the holander number is # 1331, so start looking. i had never seen one till today and stumbled across one. Also Rolls and Bentley you are correct about this trans bolting up to a nailhead, but the output shaft should be a course spline on the jeep & about 3.75" longer than a 2x2. Dave the one i found was out of a 1970 jeep p/u but the output shaft is the same length and spline as my 65 buick trans st400 i have! what do you think the deal is with that! maybe it was changed or something. Yea, sounds like someone changed the shaft to be able to use a later GM transfer case. Good deal for you tho. Just checked on the jeep cores I have & they both have the long course spline output shafts. But you will want to overhaul it anyway, so thats the time to switch shafts.I got tons of the 2x2 shafts if you need some. Dave Most of the nailhead cases in Jeeps have the fine spline short shaft used with the 4" extension housing for Buicks. the exception being the Quadratrac transfer cases. You can also find them in CJ7's until 1980. Even stranger, the Jeeps with a 350 Buick in them used the Nailhead case, with an adapter to bolt to the 350. this is the adapter that might be reversed and used to fit a BOP stick housing to a nailhead. Don't know that it would work, never tried it, May be impossible, I really don't know. The guts will interchange from any T400 to any other T400 case. there are differences. The Buick valve body will hold the trans in the gear selected, and not "blow" shift like a chevy T400.The ST400 parts will fit too, with qualifications. you have to use the ST pump with the ST convertor, and the is an orfice plug that has to go in an oil passage behind the pump at the top of the case. Also, you can use a ST 300 convertor in a ST 400 to get more stall out of the trans. The ST 400 convertor is 13", the ST 300 convertor is 11" "
A '64 to '66 401/425 starter nose will also be needed, and it has been recommended by someone that should know that the lip on the crankshaft should be removed, rather than opening up the center hole in the flex plate. I still don't understand how a flex plate can take 300 or more horsepower. Good luck, Frank
Yeah I forgot the starter, well just get one of Tom Telesco's mini starters.... as for the grinding on the crank, well I disagree with Russ on that one... I believe in enlarging the hole on the flexplate myself....
The problem with enlarging the hole on the flexplate is the bolt holes are very close to the edge and can crack the flexplate. And I am not sure on this myself, but the 364 is externally balanced like 401/425 but the balance is different and you may get a vibration with the flexplate installed incorrectly (just line up the dimple on the crank with the hole in the flexplate) or out of balance with the harmonic balancer.
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