Will a th400 work on a 401? I saw that original parts group has a 200r4 that will work but I need to get an adapter.
'64-'66 "Nails" came with a ST400 with the CORRECT bellhousing. NO NEED for adapters. Also Jeep & Rolls Royce used the "Nail" trans. which will open up your options.
I thought the X frames were all done by '64 with '65 and newer having a perimeter frame? If they ran to '67 then it should be a piece of cake to swap in a 455, just get all the '67 hooks ups and probably a '67 Riv chassis manual wouldn't hurt either. Listen to your brother, you can put a built up 455 in a '63 Riv, it won't hurt it one bit. It won't make it a race car if you do unless you plan to race it or you dump tons of $$ into the engine to get over 800 HP? A 600 HP cruiser would be just about right in that car.
http://www.gnttype.org/techarea/transmission/transtutor.html Stock they are only rated for 330 ft lbs. So stronger parts are needed.
Mine still has the Nailhead running well, but if it didn't I'd be swapping a 455 in myself. Yes, the '67 and '66 are the same, with the '66 having a nail and the '67 having a 430, so you can find some engine mounts for a '67 in theory and bolt it in to the old X-frame, but I'm sure there will still be some fabbing. Headers come to mind, but all this should be pretty straight forward with the car in it's current state and a brother with the skill set of yours. The 200-4R trans is a good choice if you get a built one, the GN guys run them behind some pretty stout stuff. The '64 on up Nailheads used a 3 speed ST400, the '63 on downs used the Dynaflow which is a 2 speed in theory, but not made to shift gears like a regular powerglide. You put it in low or hi and leave it there, it never actually "shifts". The '63 on down used a different crankshaft so an adapter is needed to bolt up a 3 speed. A later Nailhead shouldn't need it. Welcome from Montana, and start a build thread!
Yes, the 425 Nailhead and 430 Wildcat engines fit in the 66/67 second-generation Rivieras, so if you're looking to drop in the 455, just ensure all of the front-end components clear the radiator. The exhaust collectors may have some differences, but you should be able to find a shop to help fabricate any necessary parts. I don't know of anybody who's done this conversion, personally, but if you have time to piece it together with the frame completely exposed, you're in a good spot to work out any snags.
So then maybe I need to have a place rebuild that TH 400 and put it in. Just might have issues getting it to fit.
Actually I found a 200r4 from monster transmission that will handle 475 horse and 525 ft lbs torque. That's plenty.
Car weight also comes into play. That increases the stress on any transmission. The 2004R was never meant to take that kind of stress. It has to be built with all the best parts. That doesn't come cheap. I suggest you use the search function and do some research on V8. Read as much as you can and see what guys have spent. You might be surprised.
Needs an adapter anyway, perhaps a 4L80E will cost less, remember though the 4L80E need an controller for it to work properly so figure that in the cost too. There is the Gear Vendors overdrive unit as well that would bolt on the back of the TH/ST400 that would give you O/D.
One thing I forgot to mention was that the oil pan does not fit. A center sump pan MAY fir but I never tried. This actually worked really well. Cliff
Here is a pic of the motor mounts I had fanned up. Again they worked but the engine always seemed to sit a bit high and it was tilted a bit, as in the front was higher than the back. This photo also shows the th400 still in the car. Cliff