Justin,
I worked with a guy whose motto was "if it is not in the rulebook, then it is our full responsibility to go there until they tell us not to” thank you USAC.
With that being said. Sounds like your assoc is pretty tight on machining of any parts - which they would notice. So take these for what they are worth.
Make it handle. Lower your CG. Move all you can to the left. Can you offset the engine? Scale it and keep track of your tire pressures to see if you can tell a difference (never noted on a garden tractor). What is the balance front to rear, cross weight? Does it push, is it loose, you run asphalt or dirt. Offset the left had rims to the left and the right side to the left to get more left hand weight, is the 17 mag liquid cooled? Put the radiator on the left. Fill the left side with lead. Use thin oil in the rear end, make it roll with the touch of your finger, are your fronts aligned, make every thing as efficient as possible. Reduce any rotational weight as much as possible (drive line, tires, clutch), put the tractor on a diet (aluminum/carbon fibre/drill bolts/tires/wheels) Practice and time laps to see what works.
Make it breath. A dyno tuned header will give you 8-10% more hp, bore your carb, velocity stack on your carb, no filter or a k&n, take out your choke plate, thin your throttle plate (sand/surface grind it very thin), use flat screws to hold the plate to the throttle post, thin the throttle post, add a spacer or two under the carb, dont paint the head or the carb (get rid of heat), run a fuel with oxygen additive - Torco fuels ~36.00 a gallon (you have to rejet), run copper shim for head gasket, reduce the valve stem diameter, run a finless flywheel (electric fans for cooling), run a light flywheel, dry film lube all friction parts, balance the engine, index the plugs, I could give you a few more, but then I would have to shoot ya
Anybody else want to add in.....
I still have not heard from anyone on the Cub 982 frame dimesions. Anyone have a 982 out there that can help?