Something to consider.....when installing a later model 235 in a 3100 you will run into some fan/rad clearance issues as well as having the fan mounted low on the radiator and restrictions on the type and diameter of fan you can run.
I went the "short pump" route and although it gave me some additional clearance it did nothing to improve engine cooling. I found that using an ADAPTOR PLATE and using the early style pump solved all the issues. I've got some pics in my webshots album.

The adaptor plate, which sells for $40.00 on ebay or from one of the Stovebolters:

1. Allows you to mount your radiator as it was meant to be mounted.
2. Gives you adequate fan/rad clearance.
3. Moves the fan position up higher on the radiator where it can more efficiently cool you engine.
4. Eliminates V-belt/pulley/harmonic balancer clearance issues.
5. Uses the old style waterpump which is available in either 3/8 or 5/8" belt widths from your local parts houses. No pricey, special mail-order pump!
6. Allows you to use an aftermarket 6 blade 15" fan for additional air flow.
7. The early pump has the correct pulley diameter for the correct pump rotation speed. The "short pump" has you digging through junkyards trying to find a pulley off 40 year old Ford trucks. Good luck with that!!!

The "adaptor plate" installation is by no means rocket science. You do have to drill and tap two holes in the front of the block. The directions are clear and the adaptor plate itself centers the bolt holes. You don't go anywhere's near the water jacket and the cast block drills easily with a hand held battery powered drill.

Of course it's your truck and your call on which route you go. I'm sure some others will add their comments. Don't know of anybody who has used the adaptor plate who hasn't been totally satisfied with the end result.

Dave

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