I'm not sure having keel bolts replaced is a problem if it was done right. We had some freeze damage to our keel and had it sent to Mars in Canada (who made our keels) for repair. They cut out the area around the bolt and reforge a new bolt in place. Good as new.
The only thing that would perhaps be a detractor would be if they cut out bolts and patched them back in place with epoxy/glass rather than reforging lead around the new bolts. That should be readily apparent if the boat is on the dry.
But if the nuts are tight, the caulking around the nuts is in place, the joint looks sound (forms a small hairline at the attachment point every year, especially the leading edge... that's normal if there's no caulking to deal with expansion) you should be fine.
Of course you can trade the keel concerns for one of the other versions.
If you did have to rework a keel, ours went to Mars for the one keel bolt replacement for about $8k not including the yard bill for removal/install. There would never be a reason to get a brand new one unless you wanted a redesign. (Mars also sells a kit to chop off a couple feet and add wings to keep the weight but reduce the draft.)
Lots of fun info on their site.
http://marskeel.com/production/So maybe you want to take a second look at that other tartan? I can measure my bolts if it helps. The look to be all the same size but I never really paid much attention. Here's a pic, you can see the straggler all cockeyed. (and frankly, I thought we had 10 keel bolts? 4 pairs, one forward, one aft.) Ours is #299 from 1981 for comparison. Perhaps the design changed over the years. Fin keel was only 20% of the T37s leaving the factory.