Looking at a 1987 Toyota Supra Turbo

[TexasSP]

Replace it is the only option. Their are many options of what to replace it with from stock items after market parts. I would recommend looking into a head gasket meant to handle the boost you are wanting to push. Again www.suprastore.com will be a help.

Here is a nice selection of replacements.

http://www.suprastore.com/19tosumk3hea.html

Probably a good time to replace the timing belt as well while the head is off. Also remember that if you are going to upgrade the turbo you need to start looking into bigger fuel injectors and a higher capacity fuel pump. Possibly even a better oil pump and so forth. This can get expensive quick. Think RC times 100!!!