engine / gearbox installation order

New chassis is now ready for installation of the rebuilt engine and the gearbox.
I was thinking i would install the engine, all the ancillaries and see if i can get the engine running nicely, and then i would install the clutch / gearbox.
However, i have seen on some posts, it is best to install the gearbox and then mate the engine to it.
Am I going to have trouble if i go engine first?

If you have a rolling chassis can you not drop both of them in at the same time?
If not I would fit gearbox first.

I do engine first, my thinking being that there's more room to work around it. Then one gearbox at a time because it's so easy to stand astride and jiggle them. Forgot to put the clutch slave on last time, so on my back underneath it and I hate that job.

After my one and only time I’d do both together. I think there is a very good reason those more experienced than I, get the engine running out of the car first.
Those crossmembers are the issue. Accepted, mine wasn’t a bare chassis and most of the work was done on my back but getting that sodding gearbox back on the engine was a right faff and I hadn’t even taken it out. Just nudged it back it’s inch and a half so I had half a chance of getting at the bellhousing.
If I’m ever daft enough to do it again I’d definitely rebuild the whole thing and get a second pair of hands for an hour to help the lump back in as one unit.
Bleedin orible

id go engine first then use crane to manoeuvre gearbox into position use some threaded guides on bellhousing to locate and if it don’t go in turn gearbox shaft or crank to align splines, was a right sod putting new engine in to gearbox ended up buying a leveller to fit to crane made the job a lot easier

Do not do what me and a mate did, fit engine then gbox, then next day he texts me to say he has found the release beairng on the bench!