Uh I'd go out on a limb and say that there was QUITE an upgrade in quality and design with the current LSx motors, compared to similar sized GM pushrod motors from 20 years prior. You can't really make a comparison between them is all I'm saying. And I will confidently say that a modern LSx series motor will still be running strong if well maintained 20 years from now (if we still drive gasoline powered cars by then). These motors has so far proven themselves to stay strong over 150k miles in countless street cars, race cars, and hard-driven trucks. I wouldn't necessarily say the same about other GM car components...but the motor is solid.

Rx7club is a good general RX7 site especially if you're a fan of the rotary. But if you want straight up advice and tech knowledge about the V8 swap you should check out v8rx7forum.com