what are the best internal mods i can do to my supra and what would the hp from those mods be?

yeeaah.... no one knows.....

internals?? An MK3 engine/internals have been tested to hold well into the 600hp range.. Unless you plan on exceeding 600hp.. the stock 7m engine will be fine..

what year is your mk3? turbo? n/a? what kind of power do you want?

well i have a 86.5 NA; Just got a walbro 255 fuel pump an a yellow top for it.... i was kinda thinking of putting a 7mgte in there but figure i minus well run this one till it blows sooooo.... maybe internals for both the NA and turbo.
oh and the hp i would like to get is 400

if your lookin for 400hp, the easiest and probably cheapest solution would be to swap a 7m-GTE in..

But either way.. Internals in either engine are fine for 400hp