Are you talking about adding them after the fact? You sure can. Every option can be added after the fact without dealer intervention.
Like said before, it depends how worthwhile it is to any particular person on whether or not to just install all the options they want. Me, personally, I bought a 2500 tradesman with figuring out adding options specifically in mind. I have no allusions as to how much it does or doesn’t add to the value of the truck. That’s why most of us that do this keep the original parts and return the truck to stock, and sell off the upgrade parts. I wouldn’t say I turned my truck into a specific trim level, because I cherrypicked options that I wanted from all trim levels, but, it all cost me about 1/4 of what it would have been factory. I used all used parts from car-part except for adding keyless enter n go, which required a ****** rf hub and fob, so, that’s the only option that’ll stay with the truck if I sell it.
A little late to this thread but just have to jump in here. Wow, is this a topic close to my heart (and wallet). While most posting here have a 1500, I have a 2017 2500. What cab you have makes a BIG difference in just what options you could get in a heavy duty Ram. I custom ordered my 2500. The hurdle is that my Ram is a unicorn, meaning a regular cab. HD RC's are limited to two trims only. Tradesman or SLT (in 2019 its Tradesman and Big Horn). Even with the top RC trim of SLT you cannot get many of the desirable options. I can attest to Jimmy07's post. Below are options I have added, those options with the "NA" notation were not available to order on an regular cab SLT HD:
Heated and ventilated leather seats with memory (NA)
Memory Mirrors (NA)
Power passenger seat (NA)
Heated Steering Wheel (NA)
Backup camera (NA)
RA4 radio (NA)
Door bezel lights (NA)
Limited console cover (NA)
Sport door panels (very close in looks to Laramie and best looking RC panel) (NA)
Auto High Beam (NA)
Automatic temperature control (NA)
Push Button Start (NA)
20 inch wheels (NA)
Power Wagon flares (NA)
Cargo camera (this is the one option I could of ordered but did not and added it as a mod)
And NUMEROUS changes using the AlphaObd tool and probably have left off this list a half dozen more mods.
In fact my Ram is modded out. There are only 2 options left (automatic wipers and power rear slider) that I can add to it and have not pulled the trigger on them since it requires the front and rear windows to be replaced. MY severe OCD prevents me from ripping out a perfectly sealed window that does not leak.
So I built what I could not order from the factory. Did it cost me more? Maybe/probably, but I do not care since I always mod or change up my vehicles and I keep my Ram's a long time, the last one 13+ years.