underdrive pulleys on the cheap

Certainly accessories rob a lot of power. That is why the engine ratings dropped severely in the 1970's when the feds made them change the power ratings. Previously, they would run an engine on a dyno w/ no belts, supplying water and power from external sources.

I have read that some Hemi truck owners had the integral "toner ring" on the crankshaft shatter from using under-drive pulleys. That is the pickup slots for the crank sensor. Not sure why they call it that, but in this case it set up a resonance like a tuning fork, which made that name very appropriate. At least you have no such concerns.