engine / trans install question

[sawzall]

This week I hope to reinstall the engine / trans in my 29 wagon..

I have a feeling the wealth of knowledge here might serve me well..

so.. the question.

stock model a stock trans, I think i have 2 reinstall options..

1.. install the trans / bellhousing into the car, bolt up the wishbone etc and THEN install the engine into the car

or
2 assemble the engine / trans as one unit together and then slide that into the car.?

any reason why one method is superior to the other?