I've got a 87' 500  with a HPR motor running about 75hp I'm about to put back together. I plan on running Metal Tech a-arms with z 400 spindles and a no-link +4 swing arm using PEP Shocks. ( sounded simple enough) Talked to Metal Tech and he wants to know where I want the shock to mount to the swinger, I have no clue as to where or what measurement to give him? Talked to PEP and he threw a bunch of technical **** at me that I have no clue on any of it?? Anyone run a setup like this or something similar so I can get measurements and specs to get this stuff ordered and move along with my build?     Thanks for any help, Nick.

Z 400 spindles, YFZ 450 calipers, +1 a-arms, 16.5" TRX 450 shocks. What's going to be the best wheel and offset to run?

No link rear shock was pretty much a nightmare for me....used a yfz450 rear.  the angle is important.. needs to be a "rising rate" as the shock moves through its cycle,..bottom to top.  I had that shock revalved 3 times and still could not get a good action.  I would suggest using a shock that was originally designed for a no link and matching the original mount application angle exactly.... otherwise you are just throwing darts at your setup.  Your spending good money on good stuff so dont just play the guessing game.  I ended up replicating a factory linkage setup into my chassis to get a good ride.  Those linkage setups have been engineered by the best engineers the factory builders can hire .... theres a reason the factory bikes use linkage, it works..vs saving a couple pounds.

I dont know what type riding you do.  If your just on flat ground, drags or something.. then you may be ok with little to no shock action.
I ride very fast through rough whoops and need some real suspension.

I should have put in there that I'm going to run the +4 with my stock lineage. The rear end isn't my main concern. So what do you suggest motoman, I give up? I've read up on this stuff and just trying to find out from guys running this setup what works best with no binding issues so I can give Pep all my specs and move on with the build. I need wheel size and offset. Some brand of wheels run more of a true offset than others? What brand works best?

I'm running a stock length no-link swing arm on my dune bike. You didn't mention what length of PEP shock you were planning to use out back, but Alkyzilla is correct, use a shock that is designed for a no-link set-up. I was able to closely duplicate the rear geometry of a Polaris Predator 500, which is a no-link bike. I also used a Fox Podium shock from the Predator as well. If I remember correctly, that is a 19" eye to eye shock.