I just received an 'LT1' intake i got off a bloke on ebay. Said it was a ported LT1 Intake. I emailed him after i won the bidding to ask about the casting numbers (stupidly, too late right), and had no reply for that particular question.
The casting number is 12552138 which seems to be a L99 intake after doin a bit of research.

The ported intake runner dimensions are 1 1/16" x 2 1/16".
It is seems to be an an L99 casting right? However, the dimensions seem the pretty much the same as a stock lt1 intake as i read on here (after porting to an unknown extent).

Is it an intake off a 5.7L Caddy or something (as opposed to a 4.3L)??

 

I think you'll be ok. You aren't running over 350hp, right? If it is ported- and it is a good porting job- you will be fine.

Its not like the casting is inferior or something.

 

The L99 was a 4.3L LT1 in essence. It was dimensionally identical on the outside, but I believe had smaller cyl bores which made it different from the LT1. Like a 305 and 350, something along those lines. You should be alright.

Will

 

you will not have any difficulties in using this manifold

 

Thanks guys, appreciate the info. Sounds like it should work out ok.

Can i port it further to match LT1 specs? I believe i could as there is plenty of meat around the ports...