Motor is a 350 4 bolt pain 2 piece seal trans is a 700r4 which flexplate?

 

Neither the motor, the main bolts on the center 3 caps, nor the transmission care which flex plate you use.

However, the starter and exhaust might.

The smaller one (12.8") will move the starter 5/8" inboard of where the larger (14") one will locate it, which gives that much more clearance to the exhaust in that direction. However, the block MUST BE drilled for it; which blocks from before about 77 aren't.

So, I'd suggest checking your block, and if it has the inboard bolt hole, use the smaller flex plate. Otherwise you're stuck either using the larger one or drilling the bolt hole.

 

so basically the 168 will work no matter what? And if its has the holes closer to the flywheel a 153 would also work?

 

Most 350 blocks from about 75-up usually have the extra starter bolt hole. As long as you have that extra hole, just get the 305, 153 tooth flexplate that was commonly used from about 75-86. That would be your easiest solution. I'm not 100% sure that the 168 tooth flywheel will fit inside a 700r4 bellhousing, but if it does, and you only have the older, staggered starter bolt pattern, you'd need to get the big block/400 small block starter, which has the staggered bolt pattern and a smaller nosecone. Btw, the 153 tooth starters use a straight across bolt pattern, so it should be easy to tell if you have those holes when you look at the starter mounting pad on the block.