305 Mystery engine and GMC mystery axle

[JonnyTechMech]

JonnyTechMech in the house and new to this list. I’ve been cruzin this site for a week now and I’m impressed that there’s so much knowledge sharing on every level. I felt it was time to become part of it all. I’ll keep the babble to a minimal, cause I still have a lot to learn about this site. Don’t claim to know everything and plan to learn all I can from you all. As well as share, what I can. Glad you’re here and glad to be here from DFW by way of the Capital City “Austin”.

If it’s ok, I’ll dive right in.

I own an 87 GMC Fleetside recently purchased. It’s running a 305, th400 tranny. I have a few questions that maybe some of you can help me.
Have any of you seen some engines that have a dummy cavity for the mechanical fuel pump? No doubt, it’s EFI, but a mechanical fuel pump can never be installed. It’s the original engine of the truck. Is there anything special about it? It also has the four bolts that run though the valve covers.
Haven't popped the covers to check the ID yet.
The ID on the front of the block is THJ509139 and K1029FAZ.

In addition, I have a ID# on the drive axle which is BR36298 for a corporate 10 bolt. My guess, it's a 2.73. Anyone know what it could be. I’ve not found any other #'s on it. I was going to pop the Diff cover and verify the #, but the Diff bleed plug is impossible to move. I’ll start with this for now. I’ve checked 73-87.com, mortec.com and branch sites from these pages with no luck.

Thanks.

JonnnyTM