I guess you can get a lockup converter for the 47rh but no, you don't necessarily need it for the exhaust brake but it would be really nice to have.

I would recommend getting a tighter tq converter; different trans but our 91 3 speed auto has a converter and exhaust brake, the brake really didn't do a whole lot with the sloppy OEM converter. You can get better mileage with a tighter converter and even better with a lockup.

I did rip/grenade/decimate the stock NV4500 clutch in my 93! Grenading that within a few thousand miles of getting injectors and hooking the exhaust brake up was no coincidence!!

 

I just got mine last weekend too. congrats on the truck looks very good