Nothing wrong with that. The '72 probably still has the medium duty rods in it. Less inertia, a little quicker spool up. I ran mine to 6,000 rpm often. It'll have more meat in the casting for more overbore tolerance. Aaaaand, it'll have full-floating wrist pins. From '73 on they used heavy duty con rods like the 360 and press-fit wrist pins (cheaper). Does any of it matter in day-to-day street use. No. Side-by-side on a dyno, the '72 would do just a smidge better, all else being equal. You don't need ignition timing for a compression test. You do want to pull that timing chain cover and get a new gear and chain set on there. The '70's-early 80's were rife with those awful plastic-tipped gears for 318's (again, to save money). Start spinning that engine over and you could mess up. Push far enough and you will bend valves. Get a real set. Funny how that applies to so many things.
It may have already jumped timing, or is about to. Once you get that cover off you can clean it up. Should be some timing marks on it. I never used a timing light on my old '69 Charger 318. I'd just get it close so it'd start easily, then tweak so it didn't rattle when hot and under heavy throttle.
As for the cat converter, it may have had one from the factory. I know truck emissions lagged passenger car stuff quite a bit, but things were tightening up in the '80's. The light-duty trucks were beginning to get squeezed into the passenger car ranks by then. That inspector sounds like a stickler, but if it had an OEM, that's probably why.
