What your looking for is a BRF unit from a Grand National, or there is a similar, but not the same, unit in Olds 442's and Monte Carlo SS's from the mid-80's. You will also need to build the thing up to stand up to the torque of a 455. I'm having one done right now. Core BRF tranny, $200. Built up right with billet pieces, extra clutches, etc., about $1,300. Torque converter custom built for my application, $675 (OUCH!!). Then there is all the other stuff like TV cable/brackets/setup. Different yolk on driveshaft, playing with the crossmember to get it to bolt up right. Then there is the hooking up the shifter, whether column or floor. It's definitely not just a bolt-her-up and go project. You do need to have some "skills" to finess fit things to get it to work right.
It's an awesome swap if you're going with high 3 series or 4 series rear gear. My 350 turns 2200 at 70 mph with my 3.73. Any less than 3.73's and it'll lug too much I'd say. I paid a local guy to build mine. It was a mistake. I should have spent my money with Art Carr or someone like him and been done with it. Art Carr gets $2K for one that will handle the torque easily but I think thats without the convertor.
Here's something I posted on another thread: I am currently doing this swap. I have 3.73's in my car with a 28" tall rear tire. My rpm's on the highway at 70 mph will go from @3300 rpm with my TH400 down to @2250 rpm with the 200R4, according to several gear ratio calculators online. And with the slightly better gearing, I'm hoping for a little more, I mean less, at the dragstrip come Norwalk. There is an article in an older GSXtra and they took a 1970 Stage 1 that had run a best of 12.68 and swapped in a 200R4. They made no other modifications, and the car ran a 12.41. Sounds like a win-win situation to me!!
