Biggest pet peeve in teh world: People saying that Supras have V6's... grrrr
Anyway, that's quite a few KMs on it. Mine's at 197K and starting to show it. That many mods on an NA makes me wonder if its been abused.
$4500 is a pretty good price when you consider everything that's gone into it (assuming everything's in working order). Take Nashman or any of the other Supra ppl with you when you go look at it though - We know the common trouble spots.
When you turn it on, give it a couple of revs and listen for a gurgling/waterfall noise behind the dash. That means there's air in the coolant system and a common symptom of a blown head gasket.
Take off the oil cap and look for any white goop. Another sign of a BHG.
Press the brake pedal down and see if an orange light on the dash stays lit. If the taillight failure sensor has gotten wet because of a leaky hatch, it has probably shorted out.
Check the spare tire well to see if there's any water/rust there. Water commonly leaks into your trunk through the hatch.
Check the body moldings around the entire car to make sure none are "pushed out" from the body. '86-'88 Supras had metal clips that held the moldings to the body - these commonly rust and are a pain to fix.
Take it for a spin!