Was throwing belts, found 4 bolt balancer with drilled/cracked pulley. Wait. 4 bolts?

Hello! My bronco has occasionally thrown belts ever since I got it at the start of the year. I picked up a replacement radiator and fan shroud but want to solve the belt problem before replacing this stuff. When running, the water pump and crank pulleys seemed to wobble a tiny bit, so I guess that is the problem. I pulled off all of the belts, and water pump and crank pulleys and found a tiny bit of play in the water pump so I'll get that replaced. I started it up with the crank pulley off, and found the play is also present in the balancer so I figured I'd replace that. When I started looking for a replacement I found that everything was talking about a 3 bolt balancer for my year. I went back out and checked out the pulley and found it was a 3 bolt and has been drilled out to be a 4 bolt. Plus, it is cracked. So what's the deal, from looking around I guess it is probably a newer 302, so I need to pick up a 4 bolt balancer and a 4 bolt pulley?
Thanks for your help!
Andrew

edit: "fancy", huh?

The newer balancers you can get one set up to accept a 3 bolt or a 4 bolt. Mine came from Summit and it is 28 oz. and will take either pulley. Most of the new balancers on the market and aftermarket products are 4 bolt but will allow you to addapt your old pulley if you keep it.

I would definatly get a new pulley.

You check the casting numbers on your block yet? Look at the bottom of the block, just left (or right depending on which direction you crawl under the truck) of the starter. I found out my block was an '88 which explained why my new clutch would not bolt up.

Here is one solution. http://www.bcbroncos.com/bracketsandpulleys.html look down near the bottom of the page for a new balancer than is drilled for both 3 and 4 bolt pulleys. You might need a spacer also. If you need another 3 bolt pulley: http://classicbroncos.com/forums/showthread.php?t=172510

You need to take akafrankcastle's advice first. You need to find out if your engine is 28oz or 50oz imbalanced. This is a huge difference. If you put the wrong imbalanced balancer on your engine, you can destroy the crank bearings in a short time.

Check the block casting numbers.

Hi guys, thanks for he help/tips.
The block code is d2o3-6015-AB
So I guess it's a '72 Fairlane/Torino motor? I looked up a balancer on autozone and it shows a 28oz one. Unless there is a different/better way to look that up
72sport, your pulleys are the exact ones I was looking at.... when I found this.

Anything else this code tells me or that I should know about this motor as I move forward on stuff?

Thanks!!
Andrew

make sure you check the crank seal while you have everything out just in case all that play messeed up your seal.. Happened to mine when my blancer went bad. Rplaced the seal, balancer and pulley and no more play. Tight as a hat band.