Vintage racing is fun, IF you rode those things "back in the day".
IF you didn't you are in for a eye opener.
I started racing with AHRMA in 1993 and won two National Championships. It was the time of my life traveling to all the tracks across the country.
* Make sure every nut and bolt is lock tighted.
* Make sure (if you are running a down pipe) that the mounts are strong and secure.
REPLACE any wear items, cables, chain brake shoes.
Get new tires.
Re do the top end.
Rebuild the carb, pay attention to the slide, needle and seat and float.
Make sure the bottom end is tip top too.
If it has points replace them, condensor too.
Suspension: I never had "expensive" shocks until I won a set of Works Performance shocks at one race. I really couldnt tell much of a difference.
I ran a 125 Elsie.
I did beef up the forks with new springs and seals and an "x" brace on the triple clamps to help with turning and reduce flex.
I never had any DNF's because I kept my bikes in top shape. Well, I did lock up a piston at Southwick in practice (too lean) but installed my "spare" engine.
Yeah, spares, spares, spares !!
Do not be afraid to ask questions, vintage people are the best !
Have fun, don't try to jump anything big and you will have a blast.