Eyeballing it is probably going to be as close as any method without an engine in it. Because the front end uses unequal A frames and it at the upper end of the travel it's an exercise in futility to try to do and caster or camber adjustment. The toe in would be the only adjustment that would be even close at ride height, compared to the springs being extended without an engine.
I use 2, 4X4 blocks to hold a piece of angle iron up and have a couple light duty tarp straps with cord to extend them to keep tension pulling the two pieces of angle iron against the sidewall of the tire (any type of elastic to keep tension on the angle iron will work). One front of the tire and one to the rear of the tire. Use 2 tape measures to set the toe in. Center the steering wheel before you attempt to adjust the toe and you're going to have to eyeball the wheels to see if the wheels are straight ahead when you have your toe set.
FWIW, installing the engine isn't going to make the alignment any harder unless you have an A/C compressor, then it's a pretty minor obstruction to change shims. Installing the engine has zero effect on adjusting toe in as far as obstructions.
Myself, I'd wait until the engine was in to do an alignment, trying to do it while there is no engine in, is pretty much a waste of time. eyeballing the toe in would suffice for pushing it around the garage...…
