HV transformers and spark gaps

I have access to an hv broadcast transmitter plate transformer, several
transformers oou of microwave ovens, and possibly a pole pig or two. Which
would you recommend I use and why?
        Are there any drawings or plans available for a good rotary spark
gap? If so, where could I find them. And last but not least, are the g2, g3,
and g4 caps used in the output tuning stages of broadcast transmitters
suitable for use in a TC? How about vacume variable caps?

Jim Leonard