replacing old engine with new one.88Bonnie

My 88 Bonneville is getting up their in the miles. Its been a great car, I've had it since 88. Its been such a good car that I've grown atached to it. I decided to bring it back. I just spent $1800 getting a new paint job( from Red to Black ) And now its time to get to the 210,000 mile engine. It still runs good, but its lost alot of power.
I could rebuild the 3.8 V6, their great engines. But I've always been a V8 kinda person. How hard do you guys think it would be to replace the 3.8 with a eaily 90's Catillac V8? I'm pretty sure it would require the replacement of the front axle, and trans, and require some metal work to the frame and mounting points. I'm a welder, metal work dose'nt scare me. I found a 94 with rear end damage for $2300, its just got 50,000 miles. Do you guys think this is a good Idea. Or sould I consider a newer 3.8, out of a grand Prix or Bonnie. A supercharged one. I want more power. And their dose'nt seem to be much a market on late 80's pontiac 3.8 peformace parts.