If you want the look and feel of a racing tractor then as amcchevy says build it like a racer... build it to a particular class rules (including all the safety stuff) and you can't go wrong..
Most of the rules and specs and guidlines for a sanctioned racing mower deal with building a safe stable platform or chassis...that needs to come before the application of speed..
And by building to class rules, you do have the option of running in a race if you choose some day....Or selling it to a prospective racer...where a "non legal" chassis would have inherently less value...