I am in the process right now of installing my headers and new motor mounts on my sc400. My question is what is the best/safest way to support the engine if i need to remove the main support that the mounts are bolted to? can you use a jack or do you need a hoist?

 

I would use both a chain hoist and a jack to be safe. Lifting devices do fail, and you don't want to lose fingers or a hand.

 

chain hoist is a better idea. engine jack is great too.

 

we use a engine support tool such as the one in the picture at my shop. once set you can remove the k member to install headers

 

used engine hoist, but you dont have to go all the way up, just barely enough.

 

You mean you just barely had to lift it, right?

 

jack + short 2x4 under the oil pan
unbolt both studs on both mounts, lift up the motor up ( whether youre doing it legitly or ghettoly like me), install the motor mounts while lining up the little bumps on the mounts to the recessions in the motor mount brackets that`re bolted onto the motor, and lower it down slowly.
I`m sure you can leave the tranny alone, as the stock tranny mounts are soft eough to allow for enough play to lift the motor up a couple inches.