The biggest thing that TRACTOR has going against it for racing is the transaxle is very low geared and has a lot of rotating mass. You say you've read on here....have you seen anyone building out if A TRACTOR????
No, we use MOWERS !!!
Now I understand building what you have. But son what you have is not a viable racing mowchine.
Your mechanics are right, you can make that thing fast. But you'll never make it handle, you'll never make it quick, you'll never make it turn.
The worst part is, you can easily find a better chassis!!