Frank, it is thanks to posts by you and germanwheels that pushed me over the edge and down the slope to do this! So danke!
A bit of progress to report, roof has been welded on, and the internal shield for the rear roof vent - the piece that blocks water from entering the headliner/cabin from the rear vents, has been removed from the old roof and welded into the new one. Also I had Alex add some spot welds at the gutters to help bond the roof to the chassis to possibly improve chassis stiffening and strength, rather than just the crimping over it as the factory does at the gutters. Theres some body work and finishing has to be done to the roof, pillars, and gutters, prior to primer, but here below you can see the vent shield:
