Don't know how much RX7 FDs cost there but just find a cheap one so you have funds for a rebuilt ported engine with an upgraded turbo kit (so no more reliability problems and you start clean) and other upgrades (suspension,brakes,interior, respray).
It's a nice project and will probably cost you less than a Supra or FR-S and you'll be pushing over 450whp and get the perfect 50:50 handling FDs are known for...You'll struggle to find anything to match your performance in a straight line or in a track.
Of course expect 16-18mpg but anything with that amount of power should consume the same amount of fuel pretty much...
oh before someone says it - it won't break that easy if you upgrade apex seals, port the engine, do the necessary cooling upgrades and use a single turbo system you're eliminating 98% of problems as long as you maintain it properly from that point on.
I found a 1998 FD with 19,000km (11,000miles) on a new engine for 11,000$. I'd be interested to see how much FDs cost in the US