As a suggestion, Before you do anything.
I would get in contact with Rob Millinship at Leicester.
After building his Pitts (s1s) he now builds and re-builds Pitts for a living.
There is NOTHING that this guy does not know about the machine.
He would be able to tell you the best thing to do for your budget, though the Pitts is fairly notorious for not being the clearest to be heard over the RT