Hi!
Super new here and a beginner with my '73 RT3 I was gifted from my Dad (under the condition to restore it:). Anyways, the fuel in the tank is probably a few years old so I think it's a good idea to start with new fuel. Does anyone have any recommendations as to the best way to go about this? I'm assuming removing the tank to get every drop out?
Any advice is greatly appreciated, and thanks in advance!

Welcome. If your fuel smells like our rubbish in NZ them man you're in for a treat lol. Just remove tank & be careful doing 'that' as when lifting the back you could easily catch it on the steering head & damage the paint at the highest point at the front. Then on its side & fuel tap "pet cock" out & away ya go. Probably wear some throw away gloves as it's a sting you'll never get rid of--if its carrying old fuel. Personal i just get the water blaster in there & give it a flush out. Hard to get it all out the top because the filler neck steps down in a little. Others will have better up to date methods i'm sure, like soak in some magic potion. There's lots of options i've not tried.

If the old gas left varnish in the tank I've used Gunk carb cleaner (gallon can) poured in, sloshed around and let sit. Slosh it around to soak the whole inside several times to keep it wet. I use that stuff to soak carbs and gets all the varnish out. If inside of tank is rusty then I use Evaporust (5 gallon bucket) and pour it in and soak it. I know other guys here use homemade recipes that may be cheaper. The Evaporust is used to remove rust from all parts of the bike during restoration. Good luck.