"Not sure where you get this 7.625" information, but both of my LT1 cars came with a 7.5". EVERY LS1 car came with a 7.5 as well. I'm guessing that you are thinking of the oddball Borg-Warner rear that came in a few 3rd gens. Either way both are weak. Possibly with street tires, they will last a long time, but NO WAY at the track or street with a decent drag radial or a sticky DOT tire. Not a chance in hell. My friend grenaded his 10-bolt with a bone-stock LT1 car with a t56 and a set of BFG drag radials."
I'm sorry but you are wrong, in 1989 when they switched to the 28 spline axles they also switched to a 7.625" 10 bolt rear end. the Borg-Warner 9-bolt Australian based rear end and is pretty rare. As of 1989 all car and small truck (S-10) 10 bolt rear ends were the 7.625 rear end. if you dont believe me then look it up.
as for my old 355 set up, yes i ran it at the track with p275/65R15 M/t drag radials and i had the car running 12.80's. these rear ends are a weak link but there are plenty of people out there running low 11's and even 10's with these rear ends still in there car. I've seen it and so have you, you just didn't know it. While you are doing a search on the whole 7.625" rear end. do a search on how strong you can make them and how fast people are going in them. you could also ask Fbird-88 on here, i know that i have heard him talk about using the rear end as well while pushing a pretty fair amount of power.
"I could piece something together for not much more $$$ and make it much more enjoyable. IMHO vortec heads do not belong on anything over 355 cubes. They simply don't have the ability to feed it correctly. A 355 with a head flowing over 250 will crap all over a 383 on vortec heads. It would cost a lot less too being able to keep the rods, and crank and not needing as much machining. He's going to run a 650 dbl pumper which can support 450+hp, and an Edelbrock Performer RPM intake which can go well over 500hp, and then crutch the build with some tiny heads trying to feed 383 cubes."
unless you are going with used alm heads then you aren't going to get away with less than 1000-1250.00, and then to run a hyd roller cam set up will cost you 250-300 for the cam, an additial 100 over the base price for the springs, and then suposing he does not have a roller block as he mentioned, another 300 for the lifters, then another 30-50 for the bronze distributor gear for a total of 1700-2000.00, where as the RHS heads are 800.00 and a set of hyd flat tappet cam and lifters is around 200.00 for a total of 1000.00
I dont know where you get off thinking that i am recomeding the vortec heads to him when i was recomending the RHS pro action 180cc heads and yes these heads flow 258cfm @ .500", it has been independtly flow tested and published. here are their complete numbers:
RHS 180 pro action heads:
to put this into perspective here are the numbers for the out of box Brodix IK200 alm heads:
As per science, if something is able to produce the same or a greater amout of flow/air with a smaller diameter tube/runner then the air traveling in the tube/runner will have greater speed/velocity. the whole point of picking a street head is to find a head that flows as much air as possible within the lift range that you will be using while using the smallest runner possible as to creat greater velocity at the lower ranges of the lift where the motor/valves will spend the majority of their time.
"The cooling of the engine is a benefit but the main thing is the ability to up the compression ratio and not detonate. That is something that is FREE that cannot be ignored. Put an iron head on a 383 and run it at 11.5-1 and try to run pump gas. You will have to tune it pig rich and take timing out."
This does not always work, take my motor for example, i am running 11.2-.3:1 with a 106LSA cam that has an early intake closure, my dynamic compression ratio is well into the mid 9:1's and no i can not run on only pump gas when i drive on the street i have to run 1gal of 110 for every 2gal of 91-93octane. now sure i could tune it and advance the timing so far that i could run on pump gas but i would also loose around 10% or my power getting there.