Hi Eagle1, yes, we sell ARP fasteners and have actually used them on engines since just after ARP was founded decades ago. Our first ARP project was a "no-expense spared" 3-main SCCA engine. Carrillo rods and Cosworth pistons on an engine dyno, not an amateur effort. A 148hp 1.6-not bad for the '90's.
No one has more experience actually USING ARP fasteners in a roadster engine than
https://www.datsunrestorationproducts.com/. Check it out.
Truth be told, ARP's are nice, but if you know what you are doing, Nissan factory fasteners are generally fine and high quality. It has more to do with technique than the brand of fastener.
But we'll stick with your original question, and can provide much more expertise if you would like to discuss it real-time.
The difference between a stock R16 and a U20 is noticeable. 35-50HP at least, and a noticeable increase in torque, so if you buy a solid, healthy U20, you will never look back.
If you buy a tired/patched together U20, you probably will not have a great outcome (worn or failed chains, cam/rocker issues, cracked cast pistons). Yes, the cast roadster pistons ALWAYS crack eventually so keep that in mind if considering a used, not rebuilt U.
You can do a stroker too, but to actually make U20 power is quite expensive. Some folks like this approach because of the simpler design of the R/H engine. But strokers are not cheap either. A lowest cost stroker won't match U20 performance and a high performance stroker will cost about as much as a decent U20 build.
So pick your poison, R16, stroker or U20.
You might reach out to mackn367 (nick), augsburger (Glen), pjackb, cktrap here on the forum about who to listen to and their very similar experiences to yours. Nick and Glen went with an improved R after stock failures, Pjack has both R&U20 and ck is a U20 guy and makes legendary BBQ. Ck (Keith) is a good reference since he knows Glen's engine as well
A properly prepared R16, a hot stroker and certainly a warmed over U are all a lot of fun. A stock R is well, kind of a snoozer by comparison.
Most importantly - and with autoparts in general, you get what you pay for. Going to the cheapest source is rarely a good plan- and will bite you in the long run.
Photo attached for your enjoyment, yeah that's a stock design cast piston skirt failure waiting to occur.
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Prev owner said it was rebuilt and had 2000 miles on it. 
