Cross-generation pedals/brackets compatibility

[Crabass]

Hey guys, plowed through a ton of searched threads without finding the exact info I need. I have a '87 Silverado with 4.3 V6 / TH375 that I plan to swap in a big block and manual transmission. The GenV block requires the hydraulic clutch setup which I have, except for the pedal assy.
I've located a partout '89 K3500 with the hydraulic clutch / vacuum brake pedal setup like I need, as well as the big block engine mount brackets, but I don't know if the parts I need for my '87 are the same ones in that '89, considering the cross over to the next generation body from '87 to '88. The front end of the donor truck is definitely the next gen after my '87.
One serious drawback is that the prospective donor truck is a long drive from where I am. I've been looking a long time locally with zero success, and ended up finding this guy by calling yards around the area my wife has relatives in and is wanting to do the visit thing. Going there for a casual inspection of the goods just isn't in the cards.
Thanks for any info or advice.