Here's a question.....are the pistons already cut for spirolocks/snap rings? If yes then float the piston, (see if RRR will give you a set of his 273 rods he'll never use) if not, press it. For your stated goal, my opinion is it's a coin toss, your stated rpm is not all that great, nor is power level. I get low coast/budget, I don't see $325-$350 as being "inexpensive", and even with "NEW" rods you should still have the big ends checked for size. I know you can spend a whole lot more than that and I have. I was not letting coast be my guide, I was going for a whole lot more than 6500 rpm and 400 hp.
If I were you, I'd look for a an unmolested donor, pull the rods; date codes/size on the bearings will be the tell of prior work, have the big ends checked for size and if in spec put it together, I'd start with the rods in the "teener" you already have.
FWIW, my own "mean teen" as I call it, got put together with 273 rods that were pulled form one engine and poked into another, only passing thru the wash tank along the way; Desk Top Dyno said it made 450 hp and I bounced it off a 7400 rpm chip more than once.
Just my opinion............
