I bought a boat a few years back with a "fresh" 540 from a place in ohio, which is no longer in business. It had dome decent parts in it, eagle crank, rods, srp pistons, merlin heads, dart intake, dart big m block, 1050 dominator, etc. It had supposedly 20 hours on it. Dropped it in the water (after I bought it) and took it for a cruise. Ran 3500 rpm for about 8 minutes, and came to idle, and noticed 5lbs of oil pressure. To make a long story short, the engine was in need of a rebuild. The builder just bought parts, and slapped it all together. Crank tolerances were way off, ruining the bearings, main caps, carb was so fat there was a ton of gas in the oil, etc. A real mess.
I had ateco pull the engine, rebuild it, dyno it, and re-install it, the engine ran beautifully. He had the carb setup just right, and it idled like a 454 EFI after that. Both the engine, and rigging was nicely done.
Two summers ago I had ateco my heads from my 454's. Complete valve jobs, new valves, springs, seals, etc, etc. He had them done in a week or two, I picked them up and re-installed them, and took the boat for a ride. Well, being in a hurry as I usually am, put the port motor together using the old timing chain. Thought it looked good, so what the heck, its sunday, stores are closed, lets button it up right? Well, sure enough, the chain jumped while i was on the water, bending every one of my brand new intake valves! So I tore it all down again, took the heads to ateco, and bill replaced the valves in a day for me, and didnt charge me, even though it was clearly my fault for using the old chain.
Point being, Bill is a good guy, a boater, and builds some great engines. He may take a little longer than some, but you will get a quality product when its time to fork over the cash.