I have an edelbrock performer rpm carb style intake, what's the best adapter to use on it for my tbi? It is a dual plane

Their all pretty much the same, a 3/8 piece of flat steel w/ 2 big holes, 7 smaller holes. You can make one too. Use a tbi gasket as a template.

trans dapt makes them. around 40.00

I was wondering if one could be made... That's awesome. Does it have to be steel? Could you use aluminum? It doesn't have to have any special bevels or anything?

And what's the max height before it hurts your performance? Would 1" thick be too much?

You can use aluiminum, 1" thick is fine as long as you can close the hood.
I'd start by having you intake & tbi gasket handy, take a piece of cardboard & outline the carbs mounting flange, then take the tbi gasket & center it over the 4bbl. hole. Make marks where the tbi holes are, this will help you make the real one out of steel or aluiminum.
When its done bolt the adaptor to the tbi, open the throttle & look for any mismatches that might have to be clearenced. Make sure the mounting hardware is flush so it wont interfere w/ the intake. You dont need to bevel it, but it might be beneficial to open the center between the bores.
If the tbi bores overlap the intake, I'd try to grind it smooth, just don't go to far.

Making one oval vs two individual holes is what your meaning? Cool, good deal. I'll get started. The hood will be an issue right now, due to the fact I don't have my cowl hood yet, but that's due to the fact I haven't decided on ss/cowl yet. I want the pro touring hood, but it's pricey, thanks for the info

Yeah, its fun to make your own parts.

You make that one? That's awesome!! What are the 3 little holes for around the tbi chambers?

No, I didn't make that one, its just an example of an open center version.
The 3 holes are the tbi bolt pattern.

Got another question, was going to start making my adapter, marking out my template.... When I put the tbi on the intake, the tbi barrels do not set inside the carb bores, what's the trick to doing this? I don't want the lip of the intake to collect fuel, or would this not be an issue? Just curious!!

part number 2211 from summit 43 bucks

I have the TransDept one. $20.00 shipped.

Pm sent