Mk3's have basically one problem, their engines. They like to blow headgaskets at even stock boost let alone higher boost. There are remedies to the problem, however, they aren't usually worth it because the 7m-gte is an old design engine and not really worth modding if you want to see some big power. However you're lucky because in japan toyota decided to offer the 1jz-gte in the mk3 supra from 1990-1992. This is a fairly easy swap and will basically give you a baby 2jz-gte. Although it isn't nearly as powerful from the factory as the 2jz it will still give you plenty of room for mods and is quite durable. Furthermore, if you want more displacement later the 2jz shortblock will bolt right onto the 1jz head giving you a 1.5jz-gte. It's a good chassis to work with, a bit heavy from the factory but still semi-athletic.