A stock OEM converteor will probably work fine with the engine you described, if you want for $hits and giggles you could go up to a B/M holeshot 3000 or 3500rpm unit.
I also agree with earlier replies.
You need to get him some seat time, go to a coulple test and tune sessions and then go racing.
Guys at the track just love lining up to newbie(s).
Hate to see him get his butt whooped first few times out and lose interest.
Get the tree down pact, depending on how he reacts to the tree, he may need to deep stage (top light off)
Either way you look at it, it doesn't matter how fast the car is but how consistent he is on the tree and how consistent the car is.
Heres some consistency tips, for a gas burner.
A well tuned engine and a carb that isnt too rich, a shift light or shift light tach, line lock (burn outs) and slicks, are a must.
Leave on the last yellow bulb and pedal it if your ahead at the last stripe.
And always remember to be safe and have fun.
Goodluck, Cp