I think the biggest problem is getting the correct sump and ancillaries. I never worked out if the local commondore ones are correct. I'm pretty sure the sump is the wrong one and you'd need an aftermarket one.
There are engine mount plates that allow the engine to be mounted very easily. There are a few different designs that put the engine forward or higher/lower, but you don't want the sump too low. You have to work out the best comprimise.
With the gearbox, half of the problems mentioned previously still exist if you go the T56. You'll need to cut/fab the cross member, shorten the tailshaft, convert the car to hydraulic clutch master and sort out the elec/mech speedo problem. The shifter may need a little modification to get it to come up through the right place.
Using the 4 speed auto wiill solve the hyd clutch issue but I'm not 100% sure if there is enough room in the trans tunnel. Tail shaft, speedo and cross member will still be an issue, as will fitting the shifter to the console.
Then there is the wiring. Enougn places fo LSX conversions these days, so that shouldn't be too much problem to find someone to do it. You can probably get a harness from the states that will get you most of the way there.
Lastly, to get it engineered you will need all the pollution gear from what ever year the donor car is. So, charcoal cannister, cat converters etc. All that crap.
One grey area is if you use an after market block. Since they aren't from a car of any particular year, you may not require any pollution gear apart from what the car is originally specced in. (ie no cats) You'd have to investigate this further though as I haven't looked into that as much.
