Is it ok to get a valve job done on my 3000gt without rebuilding my lower block

I have an exact extra front head off another motor I use fir parts the head is good no leaks . Wud it b ok just to replace front head with the extra good one I have laying around.

I don't see a problem with doing that. Just make sure it is good and clean. No fine grit in it from just sitting around. Might want to change the valve guide seals tho before you install it.

A little bit of marking on the pistons right above the actual valve reliefs are still very much safe to use. And it’s to be expected when a pistons contacts a valve. But as long as it’s just a minor scratch and nothing is cracked. It will be ok. I see it all the time. But on the Mitsubishi 3000gt vr4 twin turbo or Dodge Stealth RT/Twin Turbo engine that the pistons contacted the valves you’re going to want to drop the oil pan and inspect the connecting rod bearings at the bottom of the pistons that contacted the valves. I saw one that blew up on the track adjustable first generation 3SX cam gears fell out of adjustment from the harmonics of using a 2 step rev limiter to build boost one of the 4 adjustable cam gears came apart and the valve destroyed the piston, bent the Connecting rod and turned the bottom half of that rod bearing into tin foil. So if you’re pushing the vr4 version of the Mitsubishi 3000gt cars then I would definitely advise you to drop the oil pan (hammer out the dent that I’m 99% sure is restricting oil flow because most mechanics were dumb enough to place the jack right under the oil pan to raise the engine to do the regular 60k maintenance). Then check the condition of the rod bearings as well as oil clearance with plasti gauge. Don’t worry about loosening and tightening the rod bolts. They are not torque to yield bolts like the head bolts are. So make sure you replace the head gasket, head bolts, and all the timing components with Genuine oem Mitsubishi parts. Especially that tensioner or you’re gunna need new heads all over again. Also if you are just replacing your bad heads with used heads from a known running car take my advice and spend the $40 to have the heads hot tank cleaned at least. If those heads came from an engine with worn engine bearings then you will have all kinds of trapped bearing material (lead flakes) that will get into your engine’s oil flow and find its way right between your crankshaft journal and rod bearing making all kinds of problems for you. Sorry for the long post. I’ve beem building race 3000gts for 25 years now.