How much money do you have? The 305 Chevy is not a good starting point. You would be much better off finding a good 350 and work with that small block. The power is only limited by the amount of money you want to spend.
They made a few versions of it. I would have to know which motor you have.
about 165 hp
Need to know the year.
About 280 horses.
305 horsepower
170hp at 4400rpm
305
Either 145 with the base 305 4bbl or 165 with the 305 Crossfire injection option
The 1985 Buick Regal did not offer the 305 V8 as an option that year.
235 horse is stock on 98 305
Advertised horsepower is : 160 HP @ 4400 RPMs.
160 hp @ 4200 rpms