As for crate motors... do you want to buy a motor from someone who paid a guy minimum wage to put together an engine you want to depend on? I went through this decision process a few months ago. I did the engine myself with the guidance of a good rebuild shop. As for the 390/360 issue, well I did the dowel trick to find what I thought was a 360 when I cracked it open it was a 352 same stroke as a 360, but a smaller bore... my point being, the dowel trick is only so helpful, to really be sure pop off the heads. but if all you have is a few minor leaks.... just fix the leaks! Now if you have a few leaks, and low oil pressure too, you might need to rebuild! When I first got my truck I had a few leaks, so I fixed the leaks and put another 2 years of driving on it. When I finally pulled the engine apart, 2 months ago, I found 2 cylinders with cracked rings, and the rear cam bearing starting to fail.. but for all intense purposes, the engine was running pretty well, the cracked rings had been causing a compression loss, and blow by, and teh cam bearing was causing low oil pressure... so you never know for sure until you see for yourself... I now have a well built bored and sleeved 360 out of my 352, with top of the line parts throughout, producing 347 bhp at the shaft I was looking for 300 Bhp but I am quite happy with it as it is. I was going to buy a crate motor for about $3000, I ended up putting about that into my motor, in a two week period, and I have a very quick truck now... So be wise and take your time make educated decisions, DO a lot of research!