It's going to cost upwards of 10K to get this car into presentable condition even if you do a lot of the work yourself.
I just did a 69 RR a short time ago. I think your number is a little low. I cranked about 8 grand worth of material into mine with these same sheet metal issues, same or less issues I should say. A pair of AMD quarter skins, a full trunk floor, trunk extensions, 1 rocker repair, 2 lower fender patches, 2 outer wheel houses, 1 AMD bumper, 1 front floor pan. Above that there was gaskets/weatherstripping, all the glass seals, a windshield, a vinyl top... the only interior work I did was a carpet and a headliner, the rest was good. I had various hardware kits for fenders, bumpers etc, I did zero mechanical work. I mean not even a brake job or a set of valve cover gaskets. I had a few decals and all the paint related products, fillers, epoxy prime, surfacing primers, sand paper, tape, color/clear.
I did everything myself so I'm only counting material cost.
This car will need everything I just listed (minus the vinyl top) plus it will need an interior, engine work, possibly trans, unknown on the other mechanicals such as a K frame rebuild. brakes, bearings/bushings, seals etc.
I think 16,000 in materials will get you close with this car, but in the end with wheels/tires, exhaust, trim work etc... 18,500 in "stuff".
If a shop does the car for you, 10,000 to 12,500 in labor. (that's with a very affordable shop rate, I'm thinking 250 hours at least on this car)
You'd be into the car for 25k if you did everything yourself. Worse case I see $37,500 with a responsible shop doing all the work, or somewhere between 25-37 if you do some or most of the work yourself.
On this car's best day, freshly restored... you have to ask yourself if you think you could get $37,000 for it.
I personally think you'd be a little upside down on this one in the end. There are drivers out there, nice driver quality cars that can be had for $18-$20k
You will blow past 20k on this car immediately and you'll just be getting started, I mean you won't even be able to see a glimmer of light at the end of the tunnel at the 20k mark.
Take that all into consideration, and if it' sounds like what you want to do and what you want to spend, then it's the right car for you.
That's my 2 cents, sorry they are such ugly pennies.