Give me some help

[RRR18]

Ok guys I fought with myself and others over and over so now it can be your turn. I'm in need of some help AND opinions. Don't hold back...really.
This is my '67. I pretty much bought it like you see apperance wise. Entire powertrain was redone by me. Everything else body and chassis was done by previous owner. It's static dropped....low.....5"front 7"rear maybe.?. It's low. Tire sizes 235 60 15 front and 275 60 15 rear. Disc brakes in front. 5 lug all around. Has a cnotch. Everything seems to be done correctly. So....should, if, or when I decide to change anything...could I? I have searched many builds on here and love the work you guys put into your trucks. I just am limited with the experience I have on wheels with backspacing and static drops and air ride. One thing I do know is that I will not cut the truck any more than the cnotch that it already has.
-Can I fit 20"s on it....if so tire size?
-Do I have to bag it to do anything else other than what it is?
I can barely get a beer can underneath the front bumper so ya it's kind of a ***** to drive, but the stance is killer to me so I put up with it. Let me know what you all think. I tried to let ya know all I can think of but I'm sure I left some info out. Thanks