Don,
By slop in the center spindle, do you mean the blade can rotate back and forth relative to the pulley? Or do you mean the entire spindle rocks back and forth? I had lots of rotating slop on my deck. The pulley is keyed to the top of the spindle with a woodruff key. In my case, the whole top of the spindle had split and key slot had widened a great deal. Only reasonable solution is a new spindle. On my older-style deck, this meant disassembling the spindle from its bearings. I believe on your deck, the entire spindle-plus-bearings assembly unbolts, and it would be easiest to replace the whole thing. If the slop is "rocking back and forth", the bearings are probably way shot -- again, replacing the spindle assembly is your most practical option. One of our sponsors could probably find you a good used spindle, or someone on the classified section. Finally, someone whos worked on your style deck may be able to give you better pointers.
Belt cover bolt heads can be removed with a grinder from the bottom side of the deck. Redrill the holes and put in new bolts. Ideally you'd tack weld these back into the deck but you're not set up for that, you could probably scrape by with epoxy. The bolts are firmly held in place by their nuts when in service, so the weld (or epoxy) just keeps them in place during belt maintenance. (The purists here will probably bite my head off for even suggesting such a thing.)
All of which give me an opportunity to post a few pictures from my own glacially slow mower deck rebuild:
I'm not sure I like the white that I used, may need to try again.
On a different topic, I spent a few hours with my new 149 this weekend. With a fresh battery, the engine purred nicely for about 10 seconds on a shot of ether, but it wouldn't run on its own. After over a year of sitting, one could pretty much count on the carburetor needing to be soaked out since I think it was put up wet. Will take care of that after the holiday travels.
While cranking the engine I was watching the hydro's output shaft. Since the tractor was abandoned because the transmission "just broke", I was hoping to see the output shaft remain still, indicating a sheared pin in the input coupler. Question: If there is a sheared pin, might the output shaft still rotate under no-load conditions due to friction?
Off to the east coast tomorrow for the holidays, won't get a chance to place with the hardware again until 2008. Happy holidays to all!