I have only seen a few factory 4 speed Burbs ,one in a junkyard that had a 292 straight six a town official used ,may have been the FD cheif's truck...was around a 1980 model...
One other similar one was a Park Dept. truck that had a 305 and it was in nice shape,someone scoffed it up at a town auction for 600 bucks..
There is one for sale in MA on CL,but its rotted badly enough that the seller says its "not roadworthy".but that did not stop him from asking 1200 "firm" for it...I think that one is an 87s model as well,has a efi 350,sm465 ..might be 8 lug too...be a good donor truck for someone who wants to converttheir Burb to a 4 speed and V8 gas engine..(like ME!)...