Stay right away from the J15 engines they came in the 1500 table top utes really old ones. They only have 3 main bearing caps and have a cast head from memory !! the A12 would
go better and last longer. I had a mate who worked in a wrecking yard & mechanical shop they where always keeping him in work either bearings wearing out or many other probs.
Stick with the A series can cop a floging and go better for longer.