One thing to keep in mind when looking for a replacement 235/261 to build is that they also came in some cars (261's in canadian production sedans and not US). Many of those have side motor mounts set ups, so you'll have to use the bellhousing and front motor mount on whatever you are getting rid of. There is a great article on Patrick's website about the swap.

'51 Chevy 1/2 ton w/'62 261, HEI, offy, fentons, dual carter/webbers, t-5 & 12 bolt posi