R:
305 V6- are they rare? No, not really. They were only used in GMC's however, from 1960 through early 1970's. Have a read here to get familiar with them:
http://6066gmcguy.org/Lots of folks on that page who have them and are trying to keep them going. The same block was used for multiple displacements including 351, 379, 401, 432 and 478 cubic inches.
Bumper- in 1965 rear bumpers were an option. Accordingly, most were dealer installed for those folks who chose them. Dealers had a lot of different styles to choose from. Post some pictures and let's see what you have?
Regards,
Steve
New Orleans
