what part of the body makes the most sense to start on

Heres is how we would handle a job like this at my shop, We would jig the body on a table, But I know thats not some thing everyone could do. So I would suggest 8 jack stand. All the same. You can pick some at Harbour Freight for cheap. Get the car leveled up on the stands. Get the door fitting pretty good.( Looks like you have done that) Cross brace both door openings and also cross brace from side to side in the rear seat pan area.
Pre drll alignment holes in the upper and lower hinges. 2 per hinge.Remove doors
Remove quarters,remove trunk pan and inner and outter wheel housings.
Trim new trunk pan for mini tubs.
Modify inner wheel house for mini tub and tack to new trunk pan
Clamp outter wheel house to tack inner and test fit quarter to outter wheel house.
If very thing fits up nice and snug weld every thing in place. When both sides are done move to the rockers. When installing rockers tack in place. re install doors using pre drilled holes in hinges to make sure you lower door gap to rocker is spot on. adjust as needed.remove doors and weld in place. then front floor pans the rear pans if needed and under seat pan if needed. When done remove bracing . reinstall doors and your ready to start body work.
Piece of cake.
Tim