What do your IAT's actually run with these various heat exchangers? Just for comparison, my last Vette with LS3, Heartbeat supercharger, and stock Magnuson h/e would run 15ish over ambient at cruise. It would go up 15-20 degrees on a 30 to 120 romp. That was running at 10psi and roughly 665rwhp. It had the stock Bosch coolant pump.
My current work truck is running a front drive Magnuson 2300 on an L33 (aluminum block 5.3L). It has a mild cam, bolt ons, and sees about 11psi. About 500rwhp. It actually has two h/e's. The stock one in front of the radiator and a full size radiator with e fans mounted in the bed. The hot intercooler coolant goes first to the front h/e, then to the big one in the bed and then back to the intercooler. The intercooler pretty much gets ambient temp coolant at all times. It holds about 4 gallons if memory serves. The intercooler pump is also an 11 gpm Jabsco unit. That's about 2.5 times the flow of the Bosch pump. IAT's run 8 to 10 degrees over ambient at cruise. They jump up 10 to 15 degrees under boost. Recovery is immediate.