B2000/Miata transmission swap

Been browsing around the interwebs looking for some more insight into a possible swap on my '86 B2K from the stock 5 speed to a Miata 5 speed. Looking to get a better gear ratio, seeing as I will never really haul anything with this truck, and I do a lot of highway driving, so the higher 5th gear would be greatly beneficial. From what I have gathered, the bellhousing and tailshaft would have to be swapped, but I haven't found any other helpful info besides that like what year trans do I need, 1.6L, 1.8L etc. ANY information that you know of would be greatly appreciated

My understanding is only the 90-91 transmissions are the same, that in 92 the started making changes between models. Which of course would back the 1.6. A 5th gear swap alone, might yield better results. I also suggest looking in to the 1st gen RX7s as a source.