The intake port and valve are the most critical part of the cylinder head combination. Gains there will improve the output of the engine regardless of the exhaust port and header configuration. Also, for what its worth my 1000 HP SOHC only uses 2" primary headers; they are stepped to 2-1/8" and then to 2-1/4", but the tubes coming out of the port are 2" OD tubes. I'm thinking if it was an 800 HP engine, I'd be best off with 1-7/8" tubes like yours. So I don't think you should let the header tube size stop you from doing some head work.