I dont think the intercooler is necessary on a 454 with the 250CID blower. Merc did the 525SC, 7.5:1 compression, 177 CID blower, iron heads, and no intercooler. They ran great at 5.5psi, and ran alot of timing in them.

The 250 series blower will be turning slower than a 177, less heat will be made.

I have 454's. GM steel cranks and rods, studded bottom end and heads. Heads are aluminum dart 308cc, 8.4:1. roller cams, dry exhaust. Running 177 weiands at 5psi. 4 seasons on them and they run great. Push my old 38 Fountain to 80mph, and pushed my 40FT 1983 Formula to 70mph. Never dynoed, but they have to be at least 600HP.