Since the later '87+ 944/951 wheels have 52.3mm offset (911s/Boxters generally have 55mm offset), you can use spacers to fit those wheels to the earlier cars. Here's a list of Porsche genuine parts that can be used:

FRONT WHEELS

PART NUMBER	QTY	DESCRIPTION
911.331.671.00	10	65mm wheel bolts (stock is 45mm) ~ $5/ea
477.501.701	2	21mm wheel spacer (came stock on rear of '82-85 944NA) ~$15-25/ea

REAR WHEEL

PART NUMBER	QTY	DESCRIPTION
901.331.671.01	10	72mm wheel bolts (stock is 45mm) ~ $5/ea (pre-'85.5 944NA should use 100mm wheel bolts here)
930.331.611.04	2	28mm wheel spacer (used on rear of 911-turbo) ~20-40/ea

OPTIONAL: OPEN-ENDED LUG-NUTS if you want to go back and forth with your old wheels ($20 total)

INSTALLATION PROCEDURE

FRONT:

- remove brake-caliper (look for two LARGE bolts holding it onto spingle)
- pry off the hub center dust cap with a screwdriver
- you'll see a clamping nut with an Allen pinch bolt. Undo that little bolt a couple of turns (line up little cut-out on the hub to access it)
- pull hub off spindle
- unbolt brake-rotor bolts and remove from hub (mark position so you can re-install with same orientation.
- place large socket on back of hub that will clear head of stud
- place socket on anvil or sturdy surface and pound out stud (into socket).
- install new longer studs and repeated with deep-reach socket on other side (thread side). This socket bracing is so you don't distort your hub and get vibrations later on.
- repack wheel bearings and install hub on spindle.
- put hub back onto spindle and adjust tightness of bearing
- put hub dust cap bac on
- reinstall brake caliper
- grind 1/4" bevel on inside of spacer to clear hub cone.

REAR on '85.5-86 944NA and '86 951 (can't remove hub because of one-piece pressed-in bearing):

- remove brake-caliper
- remove brake disc
- remove the parking-brake actuator and lower-springs AND the cable
- the hole that the cable protrudes from the trailing arm is where the studs will be removed and installed from.
- remove the parking-brake cable assembly (there's a metal clip over the pivot-pin, use needle-nose pliers to remove and DON'T lose it inside the trailing arm)
- also remove metal hole-cover as well.
- then just line up a stud with that hole and pound it out
- remove all of them. Then put the new ones in the same way (do one at a time completely)
- put the big end into the hole, line up the hub and pull it out.
- use a crowbar or big screwdriver pried against the trailing-arm to push out the stud as much as possible
- put the spacer on and use an open-ended lug-nut (flat side facing in) with an impact wrench to pull the stud fully outwards and into the hub OR
- or you can fit a deep socket over the stud and clamp together with giant C-clamp
- repeat for all the studs
- re-install the parking-brake cable & actuator assembly
- install brake rotor
- install brake caliper

REAR on pre '86 944NA

- before doing anything, loosen giant rear-axle nut
- remove brake-caliper
- remove brake disc
- remove giant rear axle nut
- remove rear axle
- place large socket on back of hub that will clear head of stud
- place socket on anvil or sturdy surface and pound out stud (into socket).
- install new longer studs and repeated with deep-reach socket on other side (thread side).
- repack wheel bearings and install axle & adjust
- install giant axle nut and really tighten it down
- install brake disc
- install brake-caliper