I haven't dealt with the 6's that much, If I'm going to put the work into my car I go all out! I would try to find a small block 351, the 302s are hard to find but they are nice! Good luck with your project, let me know how everything goes.
The answer to your question is likely at the fordsix forum. This forum is devoted to the Ford six (170, 200 and 250). There are a lot of knowledgable folks that really know these engines and don't mind sharing what they know. The link will take you the the "Mustang Corral" forum. Good luck!
The answer to your question is. The 250 will drop right in. Same block, diffrent bore and stroke, but the 200 cid acutally is a better engine. If more power is what you're after then pony up to to a V-8. I have a 66' with a 200 cid and a C-4, the C-4 will bolt up to the 170,200,250,289,302, and 351 Windsor.
A forum community dedicated to Ford Mustang owners and enthusiasts. Come join the discussion about performance, builds, modifications, reviews, engine swaps, classifieds, troubleshooting, maintenance, and more!