looking at replacing my engine with a GM crate motor and while the 383sp looks good on paper, the LSX 454 is twice the engine.

i am looking at the 11.0:1 compression engine and using a carby and 4 bbl setup.

i would look at using my spare TH400 to get it on the road initially.
1 what ignition setup is needed as its got no dizzy.
2 what adaptor do i need to fit gearbox to LSX engine.
3 do i only need engine mounts changed to bolt it in

4 pulleys,alternator brackets etc,cooling pipes advise is welcome also.

exhaust is not an issue

 

You need a specific flexplate for the TH400
Someone makes a front drive so you can put a distributor on it if you want, or MSD and Chevy sell an ignition box (probably others too) to drive the stock coils
Any Chevy bellhousing transmission will bolt on the back of an LSx engine, the aluminum ones will have two less holes used, but I think the LSX blocks have all the correct bosses tapped for transmission use.
There are any number of adapters to bolt it in. The most common are the plates that allow you to use the stock clamshells in the stock location, some places call them "setback" plates.
Holley has an accessory drive that works, or you can get something from an F-body, C5/6 Corvette, and possibly a GTO since your steering box will be on the other side (I am guessing, since you're down under) you won't have any of the fitment issues we have here with the accessory drive, but you potentially could have more. There is a guy here who did an LSx swap in Australia, not sure if he finished though