More information would be helpful here.
Using the original frame you could chase ideas such as Z'ing and dropping the front axle. You could do things like cut down the cab support framework, bringing the cab down with no modifications to the frame itself or the suspension.
You can channel the cab over the frame.
Why do you want to stay with the original frame? Do you want to keep the stock motor and motor location?
We could spill ideas here all day, but not knowing what you are trying to accomplish, and what you do not want to change, its hard to know what direction to go with those ideas...
And yes if you have a stock original truck some are going to complain when you modify it. I've tried to avoid 'hacking' any nice originals and as a result passed on buying what would likely have been the perfect truck for my COE project. Instead I bought a rusty pile of junk that will take years to repair, and once I'm done it will look nice enough they will still be offended.
I've been kicking myself since, and will likely buy the next cheap clean '54 GMC COE I see and ignore the the stock and resto guys as I cut it up.
