1958 GMC 100 Panel Build

[Ciscokid8]

Hello, I'm new to this site, but so far it looks great!
I have been around the restoration and fabrication field most of my life mostly with old Porsche restorations but for the past 8 years or so ive been fabricating off road desert race trucks. So a friend asked me if I would work on if truck for him.
Its a 58 Panel. I've been reading many threads for a few days but still have a few questions before I tear into this thing.
His requirements are as follows:
Modern chassis
New motor
Auto Trans
Power Steering
Brakes etc etc
and the Original Body

I would like to keep it the original cream color but that's the least of our concerns.

So, I have read that SKYMANGS recommended to FINE69 for his 49 to use a 87-91 S10 frame. Would that apply to this year as well? Would there be a better choice?

Other ideas on the board are going to be:

Engine: New LS EFI motor from Chevrolet. Perhaps the LC9 or LS3 (need to have/add AC)
Trans: 4L65 from Chevrolet
Rear End: Undetermined, perhaps a Ford 9"
Front Suspension: My friend hasn't made up his mind on either Bagging it or ifs/coil overs, personally id like to see this thing bagged
Rear Suspension: My friend hasn't made up his mind on either Bagging it or springs
Interior, remain as stock as possible, updated comfy seats etc

Please, throw me your thoughts or do's/dont's... I can do the work, just not familiar with what is the easiest path...

Here is it now: