I have the TF DC-3 and the appropriate retracts. Just a quick look at the retracts, and it looks like they could be easily modified to accept a regular retract servo instead of the air piston.

I could be wrong, and it's been a while.. But I think it could be done.

But back to the Spitfire, D&L retracts probably won't work for this bird. If I remember the destructions correctly, you have to flip the air piston on the retracts so it's sticking out the back. Something like that anyway. So, the D&L system might not be a viable option.