Which counterweight goes here?
 

ok a guy comes into the shop with a clean 86 gxl.
stock n/a (he wants a streetport)
n/a trans & diff
in other words completely stock

he comes out with a box and tells me he has a dilemma. see he bought light weight rotors and a light weight flywheel. but the rotors ,and the flywheel came with rear counters. they both feel they weigh the same (we have a walgreens scale and it weighs pounds not ounces) and they look the same.
usually i would put the ones that came with the rotors (since its obviousely a mazdatrix direct bolt on flywheel)
but the guy insist the "shop" he bought it from says to use the flywheel counter (so why didnt this "shop"install it)
so im using the forum to assure him the rotor ones should be used(since this has usually been the case in my old job).

the reaon why i do this is that my shop is new and small so id like to stay in buisness, and until now weve done rebuils and regular mods (ie. porting, brakes, clutches, ect.) so there are things that catch me off guard.

thanks

im going to get them weighed tomorrow but a little reassurance would be nice.
also, hes asking whether or not to use a two piece ecc shaft. i said there alot of benefits but couldnt give him any carriers other than mazdatrix.

The front and rear counterweight series must match the rotor's series.

http://www.mazdatrix.com/faq/Rcounterweights.htm

The two piece e-shaft is only appropriate if he is going to be spinning the engine for an extended period of time over 8500rpms.