The MYTH of 216/235/261 vs. 230/250/292 block length keeps coming up. There is almost NO difference in block length, period! Actually, the 230/250/292 series engines are a tiny bit SHORTER than the 235/261s. The post 1962 engines are over 20% lighter as well. See page 2 of Leo Santucci's book, a late L6 must have.
For mounting, bolt a '56 through '67 truck V-8 bell housing to your 250/292 and use the original rear mounts. The common front mount for AD trucks is the ford flathead style. Add a rear cross member if that makes you feel better or use a long, heavy automatic. See Tech Tips for info on bell housings and starters.
best wishes,
Les
