318 Mopar vs. 340 Mopar

I was also debating this. (with my 74 duster 225 slant six).

I decided to go with the 318 because, with the 340 or 360 you are going to need an 8 1/4 rear end and with a 318 you can use your stock 7 1/4 and also as mentioned all the parts and the actual motor itself are cheaper and easier to find than the 340 stuff.

hope my 2 cents helps