A couple things about the adaptor plate installation. You'll have to drill and tap a couple 3/8" holes in your block to properly secure the pump and plate. You use the adaptor plate as a pilot to get the holes properly placed. The instructions you'll get take you step by step...no guess-work involved.
If your engine is a 60 CAR engine running a larger diameter car harmonic balancer, you will overspeed the pump so you'll need to get a TRUCK balancer. If it's a 60 TRUCK engine, the TRUCK balancer will have the correct diameter pulley. A truck balancer is interchangable with a car balancer.
If you are planning to run a 3/8" belt, you would run the 53-54 truck balancer. A 5/8" belt, would require a 41-54 truck balancer. The 3/8" belt is most commonly used with an alternator, pwr steering pump and a/c compressor.
The beauty of this setup is that you can replace the pump with a stock 41-54 pump from any of your local parts suppliers. I got my pump from NAPA which offered both the 3/8 and 5/8" pulley pumps.
In addition, your pump will now be centered in the radiator, the pump will spin at the proper speed. I run a six blade 15" diameter flex fan and idled the truck for 20 minutes with the temp staying at 180 degrees.
My fan clears the harmonic balancer and has about 3/4" clearance from the radiator with it mounted in the correct factory holes. I purchased my adaptor plate from a guy on this site...Pre68Dave....great service and a quality product. This isn't necessarily an endorsement...it's a fact!!! I've got some pics of the pump w/plate on my Webshots "shoebox".I hope this helps.
