Following up on this for anyone in a similar situation - I ended up finding a guy who repairs old iPhones and thus has lots of parts, and he was able to put a l

Following up on this for anyone in a similar situation - I ended up finding a guy who repairs old iPhones and thus has lots of parts, and he was able to put a logic board with 4.3.5 in it into a shell and make a working test device for me. Wasn't cheap, but now I'm 4.3 capable!