Engine install questions

This will be my first engine/trans install. I'm working on my 70 swinger currently waiting on new ARP bell housing/flex plate bolts. Once they arrive I plan on installing the smallblock engine/transmission in one piece, in the next couple weeks when I get some free time. I am probably over thinking this but is it possible to install the headers on the engine and lower it all into the chassis or is this impossible and asking for trouble? I previously planned on lowering the engine onto the headers but thought maybe it is a possibility. I have a set of the dougs headers for the car. Also is there any issues installing the starter while everything is out of the car?

Lastly if I fill the convertor with 3qts of fluid and bolt everything up, will I lose the majority of the fluid back into the trans when the engine is tilted on an angle for installation?

Any other suggestions and tips would be appreciated. Thanks