The problem with this build is that your MX5 friend picked a turbo that is much more suited for his 4 cylinder car than it is for your 3.7L V6...he probably has plans to buy it from you as a used unit when you find out it is too small....
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So, the first thing you should do is upgrade the turbo, or buy another one just like it, and build a TT kit.
I just did some testing (exhaust back pressure) with a Precision 6266 T4 1.15 a/r (much much larger turbine that what you have) and it is just right for the stock block. The EBP vs. boost was below the 2:1 ratio....just where you want to be on a turbo build. Even with this larger turbine, 10psi of boost was no problem by 3,500rpm.
You will exceed this by about 4,500rpm with that turbo, and the entire system will choke as a result.
Take this as some friendly advice which will save you a lot of work in the long run…having to rebuild the kit for a larger turbo down the road.