I'd say the L26 is the weakest of the bunch and L67 is the strongest.
I have also seen some pretty vicious L26 powered 15+psi turbo cars hold up just fine for a very long time after the host L67 went for a crap. I think the thread is sort of off topic now though. The OP wanted to know what to do, and he should be just fine with his L32 or L67 top end on his L26 bottom end without changing the whole thing.