I always run 29-31 in an engine set up like that.

I had a 468 like that that did 700 with 8lbs of boost and an intercooler.

no reason for there not to be 550+- in that engine.

I agree, I would lower the boost to 5-6lbs and run the timing at least 28 degrees. This engine has cast internals correct? Was the timing set at 21 degrees to avoid punishing the pistons? Any pre ignition is almost instant death for cast pistons.

As stated, get that timing up before you melt the exhaust valves. Luckily its in a truck, if it were in a boat, it probably wouldnt have lasted very long.

The only thing i can see holding you back some is the cast iron oval ports, especially the truck heads with small ports and valves. Of course the cam plays a huge role.

Measure your pulleys, or figure out how fast your turning the blower to get that boost. You can tell alot on how effiecient a engine is based on that. I can tell you to get 6.5psi on my 454's, i had to drive the blower at 1.83:1. A buddy of mine had the blowers on his 509's originally. The pulley that made 5psi on his 509, also made 5psi on my 454. That tells me my 454 probably made as much power as his larger CI engine. Theoretically, his 5psi pulley, should have made at least 7psi on my engines, but not so.

To get 6.5-7psi, I had a 3.0" top pulley, with a 5.5" bottom pulley. 5psi was with a 3.25" top pulley I believe.

I had the 6" bottom from teague and the 3" top. 6000 rpms sounded like death under the hatch. Never heard one scream so loud. It was great.

Do you know what pistons are in the engine? and valves in the heads?

I dont know the internals im guessing nothing much the E85 lets you get away with more than gas i do know , i do know it has 2 bolt mains , what i did figure today is the dist is advancing the timing it is not locked its possible the advance was frozen up as i belive that happens if its been sittting for a while .... it was advancing to like 31 deg from the initial 21 i had set , it is not a performance dist so i may add one this spring with the proper curve , i did bump the timing to 25 inital and it advances up to around 35+ or - a degree and took a quick spin around the block definitely felt a difference ....... ive had good luck with the way it was running with the higher boost and the E85 where the timing was at i mean it felt like it was making some power as it gets up moving pretty fast for a big truck esp with the tire size .......im gonna have to dyno it just for fun and ill post what the results are ....i was figuring at least 500 crank HP i like to be more conservative with guestimates until you have a slip or a dyno sheet i was just curious what similar setups were seeing of course we all like to belive that the motor makes a bazillion HP and knocks the earth of its axis when its throttled but real world numbers often burst that balloon .. when i had my Buick GN it made 530 HP to the wheels and 710 lbs tq on a mustang chassis dyno , which i was told is often refered to as " The Heartbreaker " as it reads more real numbers than the dynojet one ...at 3000 lbs with driver it ran pretty good for a street car .....Thx Guys for the input