360 Questions

They were used in trucks from 71 thru present, (at least I think they still use them). Also used in many different cars from 72 thru about 80 I think?? The 71-90 engines were considered LA series and the 91 up are Magnum series. The 71-73 models used a different rear main bearing and seal but not sure what the diff. is. The real early blocks were thick walled units that were basically a 340 not bored out as much. There's alot of hear-say on this matter as to what year they ended the thick wall units but I'd say if your looking for a block to bore over more than .030 you need a 71 or 72 unit. 73 thick wall units are very iffy as to their existance. The 86 on up blocks are roller cam engines so that's a plus if you want to run a roller cam.

As to your question about what is the best year. I guess the early thick wall ones would be the best but good luck finding one and you better get a 71 or 72 to make sure it's really a thick wall unit.