The ZZ572 620 HP motor has uses the GEN VI dogbone/spider set up.

and uses Chevrolet Performance Lifter # 17120060

I'm not sure if available in a kit or not. Or just indvidual.

see here for parts breakdown:
http://www.chevrolet.com/content/dam...ications-1.pdf

BTW: I forgot to add...I'm not sure if above lifter is what you are looking for, but very well could be, so that's why I posted the above info.

My Lingenfelter engines had the stock GM lifters in them for 17 years w/ .640/623 lift and no problems. There is more to the equation than just the lift of the cam, base circle comes into play also.

Pretty sure these are the ones you would want if you go GM.

https://www.summitracing.com/parts/nal-12371056
http://www.gmperformancemotor.com/parts/12371056.html

That is the same kit that I use. Eddie Young told me that as long as the top of the lifter doesn't fall below the dogbone on the base circle and as long as it doesn't hit the dogbone at max lift, that they will work fine. I installed a set on my 575SCI 4 years ago and 160 hrs ago and they are working fine. Couldn't ask for them to be more trouble free. Now, the guys at Bullet cams told me that about 400# spring pressure is all that they can handle. Might be accurate, might not be.

At what point is it recommended to go with the lifters with the dog bones? My stock 502 doesn't have them and I'm just getting ready to yank the motor to put in the 525EFI cam(236º/244º @.050" .610"/.632" Lift Valve
114º LSA ), but if it involves new lifters then I'd rather wait for a full refresh.

Is it a gen 5? That would be flat tappet. All stock gen 6 502s to my knowledge have dog bone lifters.

Huh. It's a Gen VI GM ZZ502 build. I didn't have a super close look at them but at a glance I was surprised to not see them.

Yours has dog bones Stan. I installed them.

Well there ya go, lol. Thanks VC!

There's no clearance issues here, the Merc 525 is based of the gen 6 502 and they run the dog bone hold downs with that cam.