Rebuild time!!

[2ndnissan]

My daughters '90 240 has finally had the dreaded blown head gasket. Car was starting and would run rough for a few seconds then just die. I had fiddled with the timing a little and it didn't really help. It ran for a few minutes Friday but I never could get the idle to smooth out. This morning i finally decided to pull the head and check. Bingo!After releasing three of the bolts a steady stream of water started to trickle out between the block and head. Sure enough..water was standing in the cylinders. The good thing is1) the rings seemed to still be ok and water was not leaking out quickly,,2)pistons were still moving freely and cylinders weren't scraped and no cracks in the cylinders. 3) the head seemed to be in pretty good shape...no bent valvesI plan to do a complete rebuild from top to bottom. This motor will never be raced or drifted/auto x'ed. It's strictly a daily driver. I am on a tight budget but still want good parts that would make this motor last another 100,000 miles. This is the plan:

1)Pull engine and get the block tanked and heads rebuilt. There was a LOT of rusty water so I'm sure passages might be blocked. Any recommendations on springs to use? Potential turboing in the future..three four years. Would I neceassarily have to change the valves if none are bent? The head will be checked for warping for sure.

2)It doesn't seem as if I'll have to go oversized on pistons ,rings or bearings at this point. If I do need to, whats the most it can be overbored safely?

3)Should I change the heater core considering the rusty water? No leaks on the floor board inside but I don't want anything contaminating this cooling sytem for a LONG time....

4)Pistons and rings will still be replaced as well as the main bearings. What's the best brand /place to get those?

5) will I have to pretty much piece together a rebuild kit or does one of the sponsors have a complete one available ?

6)Tried to talk her into a 5 spd swap but no go. So all of this work is going into an auto car..sigh,,,,,