depends what you want to do with the car
I'll probably get flamed for this but here goes.
If you're planing to us it on the track where mid to high revs are constantly the go then in my own opinion you'd have to upgrade the internals, oil pump, maybe even the block, etc etc etc. Hey you could get 1000 hp but its not going to last to long in std form with track work. With what the seller told you about the upgrades to 550+ then yeah go for it. I reckon it would handle it ok as long as all is good with the eng. at the moment. Of coarse there will be exceptions out there on the hp. issue. I can feel them writing now. Pretty much all comes down to how much dough you want to spend now rather than how much your prepared to spend fixing it later. So many variables. What to do? m2c
Mick
ps. good article in 'High Performance Imports' magazine no. 80 with a comparison with 2jz.
worth reading.