I have always removed engine and tranny as one unit. But now just need to work on the engine. How difficult is it to remove just the engine and would I really save any time in the long run??

To me, its the only way to do it. You do have to support the transmission, but pulling them out together is a paint scratching proposition.

In addition, when pulling them out together, you need a lot of ceiling height which some places don't have.

I unbolt the intake manifold, and have made a "lifter" whose pickup point is about 2" above the cam in the valley. I have had many engine changes over the years and don't even have to take the hood off.

With an automatic transmission it's easy. With a standard shift, not so easy.

For many years as profession, as well as hobby, have taken engines out the top in almost all cases. That whole take it out the bottom thing is a waste if you're just doing engine.

I just pulled the engine in my Bee today. I left the trans in the car. (auto) I don't have a lift so my car is on jack stands so I can get under it. I don't think my engine hoist would be able to lift both high enough to clear the fenders. The only tough bolt for me was the passenger side trans bolt slightly below the head. I needed a bent handle adjustable head ratchet to get that one. Everything else is fairly easy.

I pull the trans and then the motor. That way less chance of tearing the paint up. When I put the last one in the dart I went in from the top with the hood on then trans after

just pulled mine in the charger, left the trans in the car, put 2 bolts on the front side of the bellhousing & put a cross bar to hold the trans up.

I think I may have pulled one or two ever with the trans attached, not much fun by yourself. I've done probably 100s just engine and leaving trans in... hardest part is getting to some of the bellhousing bolts, but not that difficult in older cars. If it's a manual trans, I would pull the trans out first to save a lot of hassle later on.

I had a terrible time pulling the 4-speed first on my Bee. The top 2 transmission to bellhousing bolts were an absolute nightmare. So I started pulling and installing them together. I don't remember the top two bolts being such a complete pain when I had a factory bell on it.

In the old days before # matching, the top radiator support was cut out, bolted back in with straps. Much easier to get engine-trans out and back in together.
If you have a lift, pull separately. I just finished rolling around on the floor yesterday pulling the trans from my Ram Van, every muscle and joint is killing me, getting to old for this. Bad part, I gotta rebuild and put it back! But not for awhile. LOL