I'd throw a guess of upper 300's-400 HP. My old combo was somewhat similar to yours and ran pretty decent for what it was:
-408 c.i.
-stock heads (ported and polished)
-1.6 stamped rockers
-comp 280H hydraulic cam
-flat top pistons
-dual plan air gap intake
-750 mighty demon carb
i had a TH350 with a 2800-3200 stall, which stalled in the upper portion of that range, a 4.10 gear (8.5 rear end with a spool), and it ran 11.7's in the 1/4 mile. I drove it on the street for a very short period of time, before making it a bracket only car. I don't think I'd want to be on the highway too long with the 4.10 gear. It was a pretty fun combo, and it sounds like you have something similar.