My '75 duster 318

Welcome aboard!!And what a nice Duster you have there
I would really take the roofing patch off and find someone to weld in metal to fix the floor.As for the color of the carI had a vision of what it could look like lol,you could go with black on the dash,dashpad,maybe get a black aftermarket wheel,black carpet,black kick panels,cover the headline in black fabric,basically everything black,but find matching vinyl for your door and rear panel,and arm rests that match the green on your seat covers.The outside,you could maybe go with Sassy Grass Green,with black side stripes(like on the 340 Dusters),black tail light panel stripes,and wheels,some Torque Thrusts with the blacked out centers.black out the grill too maybe
And for the hood,black it out with a semi gloss with a hood scoop like the one on this Dart Hope this kinda gave you the same vision I got,lol
You said you are on a budget and the body on that car looks pretty good so you have a good start there.