Shaggs
Nice looking truck, no rust. I live in the land of rust, so something that age would have been dead years ago. My 1991 is considered old here (not ancient, but most 1991's around here are rusted or repaired) due as much to the climate as the tons of salt they pile on the roads in the winter.
My C223 was rated at 58hp by GM back in it's day, but Jerry Lemond will tell you they were rated slightly higer. I believe Jerry. What is the C190 rated at? I know I've read it somewhere, but don't remember.
As far as performance increase, it is always a question of gains verses $$, especially with an older, not-so-common engine, unlike a chev 350 for instance, where hop-up parts are available almost anywhere. My truck is probably the slowest around here. Our shop just got a new Ford F350 pick-up, with a 360hp diesel. However, fuel just took a jump to $1.42 L, so all that hp is gonna cost. Horsepower never comes for free.
I'll stick with the pokey old diesel Sonoma.