You're right, you probably can't return it, so you'll have to eat the cost and buy an appropriate sized gasket. From what I've read, these engines are quite picky about combustion chamber size, so if you run your current gasket you're setting yourself up for failure.

You have opinions/experiences from knowledgeable Supra community members (see thread referenced earlier), and they're saying the build you're proposing is far from ideal. To me, it's a no-brainer; spend the couple hundred bucks now so you don't have to spend the couple thousand later.

Alright so I have .4318mm off the head, .1524mm off the block. Stock gasket is 1.37mm. So adding that up the gasket would have to be 1.9542mm. You really think I can't get away with a 1.4mm MHG? Just clarifying here cause a 2.0mm MHG would roughly be another 185 bucks. Then I have a 1.4mm gasket laying around.

Custom order a .6mm shim? Don't know who has one available for the 7M. Otherwise you may be able to get at least half of the money on the 1.4 by selling it used.