I have a 352 that is stock, and it like 15+ initial and 36 total. I started it up this morning after I fixed my distributer, and it fired up on the first shot.

I imagine my truck has a stock low compression rebuild with about 8.5 compression.

So you 390 should like the same unless you have added lots of copmpression or cam. I live in SoCal about 100ft above sea level.