Simon,
The
oil ring / wrist pin relationship on a 331 je / srp piston is a non issue. The motor will not burn excessive
oil. There are a lot of guys running this combination much harder than you ever will with no problems of burning excessive
oil. You may be confused with the 347 combination which has had problems due to rod angle under road race type conditions. 331 is much more durable for extended high rpm abuse.
Don't sacrifice your rod length for a myth. The 5.315" rod was the hot set up in 69 and 70 as used in conjuction with the boss 302... trans-am rod length. It gave a better rod ratio / more dwell time than the shorter rods. The 5.4" rod is better yet, in fact it is very good. Run the 5.4" with je's and you won't have a problem. Oh yes, get an engine builder to help you. Did I mention that?
Best of luck, John