Pat, check your ignition timing....you may need a wee bit more advance. Retarded iggy timing will make the engine run hotter than it should.
How confident are in in your temp gauge? Most electric gauges aren't all that accurate. 230*+ temps should have that thing puking the coolant out once you turn the engine off. If you can, try comparing the gauge temp to actual engine temp with an infrared temp gun....see if the engine is actually getting that hot.
Running with no t-stat at all will work as a test, but it's not good for continued driving. The t-stat does more than try to regulate coolant temps...it also regulates coolant flow thru the raditator. If the coolant flows thru the rad too fast, it won't have time to actually transfer coolant heat to the air. No t-stat can also cause leaks and possibly breaks/cracks in the rad, with the coolant gushing right out of the engine into the hose with no restriction at all. If you don't want to run with a t-sat all summer, then get your old t-stat, and cut the center tower part(with the "pill") out, and then reinstall just the outer part, to use as a restrictor.
Of course, all of this is assuming the rad is clean inside
and out, and the seals for the shroud are in place. Also, since you mentioned the aftermarket pulleys, do you know if they slow down the water pump speed? That could be an issue, too.
______________
Joel Adams
C3VR Lifetime Member #56
My Link
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"