Not trying to shit you
And by no means am I trying to insult you... I'm just saying 7 years and 6 motors might be some really crap luck. I've had 4 engines (only popped one, two were crap and one was fine, I just sold it) in 10 years and after the last build I learned what to do better on the next one (thus the RE cosmo engine). I think you've got a great setup there and if you rebuild the motor one more time, either stud or pin it.. there is an obvious weak point.
With the experience you've gained in all the RE engines, you should be able to pull that engine out and tear it down pretty quick... give it one more shot
You can have a solid RE engine much sooner then a V8. Sorry if I'm a hater... but I've always been a purist.
And for the record, I love V8s. In a truck. Or a boat.
Good luck on whatever direction you take man....