i was wondering if i put a z6 head ona stock 91 dx block if it would put me around the same hp as a stock z6 motor or d15 vtec

 

Tuned properly, yes.
Best drive-out-of-your-garage-after-the-swap tuning is to use a stock p28 ecu and do an obd-1 conversion. It adds a little bit up front in expense but it will save you hours of tuning headaches and probably save you money in the long run.
If that's not tuneable enough for you, you can always chip the P28 later.