I have done a few in my day, even in the B2K's, the entire project is a gotcha, especially your wallet, lol, because nothing is ever plug and play or off the shelf when it comes to engine swaps.
My best advice is be prepared to have the truck down for a while and get to know some of your local fab shops or CNC owners. Those will be your best friends. Always the most challenging parts are the front engine mounts, the transmission mounts, drive shaft, rear end and the exhaust.
Personally I would do the job right with a stock 12a or 13B, enjoy it for a while while you set money aside for a turbo upgrade or such. With the rotary high horsepower set ups you'll need more fab work for things like intercoolers, external oil coolers and most importantly piping for turbos and exhausts. Unless you have the cash to throw at this all at once do it that way. This will ensure you will not get burnt out weekend after weekend wishing you had never started this in the first place.
My rotary pick ups were a blast to drive. In their day They were smoking 5.0L mustangs and that was fun. I loved having to use modified motorcycle tachs because the ones available at the time would not rev beyond 8K.
The ones I built were;
-Suzuki Samurai
-Mitsubishi Pup, (I think)
-Nissan Hardbody
-Mazda B2k extra cab
All had Ford rear ends because I inevitably melted the stock rear ends in no time.
