can i install it with the distributor on?

I like that painters tape trick! Nice. On on the block and distributor base, one where the rotor is under the cap & on the cap. Good idea!

Otherwise, motor and trans installed as a unit? No problem. Just keep that engines front naked. Even the water pump taken off is a huge gain in space and easy to do, on & off.
That's how I did my big block in my '71 Duster. Oh, no radiator as well.