Welcome to the 'Bolt Garfunk18! Can you post a pic of the frame? There is one way i can tell you without seeing it, and that's in how the front suspension is mounted. The pre-'87 (and up to '91 on Suburban) has the boltd in cradle, as shown in the link you posted. The '88 (GMT400 chassis) does not have a removable crossmember, and the upper control arms mount into integral tabs on the frame. They also use a cam bolt style adjustment (although '88-early '89s might not have the bolts if they've never been aligned) as opposed to the shim type adjustments of the older trucks. I have heard of using the '63-'87 cradle to get an independent front end, but it is a little wide for the AD truck, so the tires might stick out past the femders a bit. Another option that is very popular with converting the AD body truck is to use an S10 long wheelbase truck chassis. You would use the entire chassis. The wheelbase is 117", about 2" longer than the original, but it corrects the problem on the AD body having the wheels 2" too far forward in the rear fenderwells. Also makes for easy V8 upgrades, using the many S10 V8 kits. You can also gain 4 wheel disk brakes, if you use the right OE parts, without having to deal with aftermarket parts.
