Go for a standard 180 head (makes cam choice easier for you)   Ditch the vvt (personally prefer solid pulleys). Though the S80 can drive the vvt so may be worth trying to make it work for you. There are very cheap adjustable pullies for these.   Satchel engineering offer an inlet I think   45s may be a bit small for the cc.   I recently sold a crank to Andy on here, his issue after removing the drive for the balance shafts on the crank was the balance of the whole crank.   There is an oil feed to the shafts which needs blocking off.   Iirc the windage tray bolts to the balance shafts so you'd need to look at how to mount that better.   Worth fitting a new oil pump as the ew12 doesn't rev past 5.8k in standard trim iirc   You are also best to look at the breather issues people have when using the non factory inlet. I have seen a good alternative when using a satchel inlet, a bespoke adaptation and some careful thinking should see you well on the breathers and the return to the sump.   Iirc the ew12 has 1 of the 2 large oil return galleries blocked by head gasket so may be worth looking to open up the oil return for the 2nd. I don't think the ew10 has a large enough bore.   The ew12 pistons are very light in standard trim, but they have lower compression due to cut outs to the piston. If building from scratch it's worth fitting custom pistons and rods.   I'm 99% sure the block height difference is below the mounting point of the engine, so both ew10 and ew12 sit at same height in the bay, just sump is 20mm or so lower for the ew12, so ew10 exhaust options should work. Not offered up a standard ew10 manifold yet to look at downpipe location etc...   I'll be using a  206 gti 180 gearbox, with a 307 sport final drive. The 206 clutch and flywheel and probably convert to hydraulic clutch or bolt on the bits to convert it to a cable clutch. The gearlinkage unbolts to allow standard 205/309/306 etc... items