LOL don't just REPLACE the head gasket, without proper inspection...
for all we know there could be hair line fractures in the head, or it could be warped without repair...
follow the TSRM and you will be good.:
http://www.cygnusx1.net/Supra/Librar....aspx?S=EM&P=1
as far as head bolts go strait edge them and inspect your threads. clean the threads in your block to insure proper torque
hate to bring it back but compression test will tell all. 14psi max difference between cylinders.
as for your pistons.
83mm is stock??
1982 5mges have 8.8:1
1984 and up get 9.2:1
i ran a quick search on ebay celicasupra.com and a few other sites and came up with nothing on trd pistons, i would say you have some rare shit, considering stock 5mge pistons are discontinued.
if your planning on using them i would go for a block and head shave and metal 7mgte head gasket.
if toyota did infact make your pistons, there quality and i would not doubt there reliability, but from what i understand stock hg with 9.2:1 pistons was designed for around 180psi, your gona be pushin over 200psi with those pistons, and a aftermarket headgasket would be the solution.