For equal or less money that what it would cost to build a 250HP you could swap in a late model GM 4200 Vortec 6 and get either 275 or 290HP with 100% stock reliability.
I had a well built 292 in my truck - got 14 mpg around town 16 on the highway. Swapped in a stock 4200 - mileage jumped to 21 around town and 24 highway with no other changes.
Tom bought the 292 and it eventually was the dyno mule that he did all the 292 dyno work with. After 500+ pulls it was still running strong to give you an idea how well built it was.
