Mars keel has an aftermarket mod for fin keels that might be cheaper for you than a keel replacement.
http://marskeel.com/services/1Here's the PDF off the site showing a dude doing his own refit.
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File comment: Cruising World keel refit.
Refit.pdf [142.71 KB]
Downloaded 31 times Mars did make all the T37 keels. They should be able to tell you how much weight 1'7" of you keel might weight. (that's what you need to get to 5' draft.) Sounds like this is your best deal though. you're with in their 12" to 24" range.
At the same time, it was a little over $3k to transport our fin keel from IL to Mars, replace a bolt, and ship it back. I wonder if they have molds for a shoal keel for the T37 and how much a swap would cost? Or even if it fits on the fairing?