I need BIG BLOCK advice

[imdarren]

Need advice. What should I do....
I have a buddy that wants to sell me his 454. I dont have all the details, but here are some general things.
1)Its bored ?? over.
2)Its balanced
3)Forged steel crank built by ??
4)Big connecting rods built by ??
5)Its a mid 70's truck block
6)Small Hi Torque starter
7)ported iron heads (I think pocket ported done by himself)
8)B&M supercharger (not sure what model. But its one of those ones that Holley owns now)
Figured to be slightly over 500HP.
All for $4,800. And he said I can pay him over the next 12 months or so. I typically dont like to do deals like that though however with friends.

OR

Buy a new GMPP 454HO for $4500
1)Forged steel crank
2)Roller Cam
3)newer Gen motor with one peice main seal, better timing cover, and all other newer designs built into these motors.
4)The motor is new with a warranty. Not "rebuilt and bored over"
5)Advertised as 425HP
6)Pay money to a dealership, and not mess up a friendship with some vague / fuzzy pay schedule

Thanks for any advice!

Darren