I can speak to Keith Craft and Barry @ Survival Motorsports. Both are top notch builders that I would not hesitate to give may business to. (FWIW.. I've made major purchases with both) Keith is a board sponsor and Barry has had a lot of the top FE motors at the "Engine Masters" competition. This is not to say that these are the ONLY good ones, just the one's I've experience with.
I'd be careful of these Epay "hogged out" 390 blocks. Who's to say that the sonic test you received was legit and actually done on YOUR block, the one you're buying??
It's really easy to keep a good sonic test on file and ship a copy of it out with every engine sold. There's been a lot of horror stories, rings won't seal and the engine constantly overheats cause cylinder walls are paper thin. You just can't look at it and tell.
Best advice I can give... Choose your builder wisely and listen to all the board members' experiences..
Dave