I'm looking into swapping a V8 into an RX7 and would really love it to be a 6spd. I'm trying to build up a motor first before the swap though and I've got 3 options.

1...I can use an LT1, but the downside is that it's a good deal more expensive to build one up.

2...I've can pick up a 350 4 bolt block (1 piece RMS) and start from there.

3... I've also got a deal on a 400 SBC 2 bolt block (2 piece RMS).

I'm wondering since the LT1 uses the same bell hosing pattern will a T56 bolt up to the 350 or 400 blocks and everything line up? The one problem I might see is the flywheel won't work with the 400 because of the 2 piece RMS. Could that be solved with a different flywheel or a 1 piece RMS conversion?

 

You might want to check with Andrew on pro-touring.com. He had an LS1 in an RX7 (recently damaged by extremely hard telephone pole). He can probably answer a lot of your fitment questions.

 

McCleod makes a bellhousing that will bolt-up to any SBC and will accept a multitude of transmissions (including T56 ). I'm pretty sure that guys who have bolted T56's to Gen-I SBC's use the McCleod bellhousing and LS1 generation T56's, because of the more conventional "push-type" clutch, instead of the "unique" (read: expensive) LT1 "pull-type".

IMO, I'd go with the 4-bolt 350 ... in a car like an RX-7, I'm sure it'll provide more than enough power, and parts are more common for 350's than they are for 400's. As well, because 350's use a neutral balanced flywheel, vs. the 400's requiring a balanced (weighted) flywheel, I think that would be easier to match up parts, since you may be retro-fitting some parts (ie: Gen-I engine, Gen-III transmission).

That's my $.02 for you .

Edit: obviously if you decided to go with the LT1 engine (that would be more tedious to hook-up initially, due to the extra wiring/computer, etc., although it would have the benefits of EFI) you would have to use the LT1 T56 . Only if you're going for a Gen-I SBC (vs. LT1/Gen-II) was I recommending the LS1 (Gen-III) T56 .