I can tell you what I did, and it worked out for me.
1st: body work (including rust repair), priming, blocking, wet sanding prior to paint
2nd: underbody/frame paint, engine compartment paint
3rd: All mechanical work - engine, brakes, suspension, drivetrain, etc.
4th: partial interior - just insulation (I used Dynamat "clone"), fitting of hvac system, brake pedals, accelerator pedal, trans linkage
5th: color coat and clear coat on door jambs, inside cowl and fenders, underneath hood and trunk
6th: install all sheet metal except front bumper and front valance - align panels
7th: clean, prep - then shoot sealer, base coats, clear coats
8th: wet sand, cut and buff paint
9th: Complete electrical system including all wiring, dash
10th: final assembly - remaining interior (carpet, seats, headliner, glass, door panels, etc.)
bumpers, valance, external lights, external trim
That worked for me, but it's sure not the "only" way to do it.