C20 saddle tanks question

[earl84]

The other thread about gas tank regret got me thinking. The 66 C20 I bought has hole in the side of the bed for saddle tank filler caps, but, unfortunately, just holes. Kind of thinking of maybe just putting saddle tanks there and removing the in-cab tank, instead of putting a tank back where the spare would normally be under the bed. Kind of the best of both worlds. Anyone know if later model tanks fit, like from 73-87? I have seen some on Craigslist, but just not in position to buy right now, priority is getting it on the road for now.
Anyone have experience with doing this? Is it too much work or too hard for not enough return? Are they problematic to operate? Do they have sending units to monitor fuel level? Anything else you can think of?
Maybe I should start a really slow build thread. Just working out of my driveway with minimal tools and knowledge, pretty much learning as I go. This board is amazing for information and great guys who share it, thanks.