motor rebuild

[derrickmd18 at juno.com (der flo)]

I was out racing my car last night and all of a sudden it started
shooting smoke out the tail pipe. when I saw this I let off and pulled
over and cut the car off. checked everything and it didn't look like the
headgasket was blown or anything so i let it sit for 10 mins then started
it up. lightly smoked a few seconds then it was ok. I drove the car home
and it didn't smoke once. I'm thinking my rings are shot. I have a spare
motor in my garage and I have a headgasket kit. I'm thinking if I should
rebuild the motor that in my car or rebuild my spare motor and drop it
in. What do u guys think?