Need help on the conversion from EFI to carb on a 454 out of a 99 suburban. What manifold would be best and where to get it. and any other info on other modifications i would need to do would be very helpful  

I'm not sure which manifold would work best, But i do like ordering parts through Summitt Racing. Not sure if you're going to have to change your heads or not. But the distributor will have to be changed. And you'll have to find a way of running a lower fuel pressure, either by using an aftermarket regulator or changing the fuel pump.