Belated Merry Christmas.
Good call on the 1990 "Shaguar" XJ6 fan clutch. I used one of those with my small block setup. It gave me more room with a thicker aluminum radiator. As an alternate, the ford countour "mondeo" electric fan setup seems to be pretty compact and work well. Theres a thread on Fabo for that.
Remember that on hard acceleration the engine can move forward in its mounts up to 1/2" to 3/4" unless your using polyurethane and or 73 up style spool mounts. Make sure you have adequate clearance here or your fan will eat the radiator. Check your clearance at fan blade tip to radiator at the bottom since the engine is angled down at the back and is closer to the radiator at the bottom.
There is also a really cool thread on Fabo about using electric power steering setup off a Toyota Yaris steering column. The thread entails modding your existing steering column to fit the yaris electric power steering unit under the dash. Then using a smaller manual steering box under the bonnet with a universal joint and shaft, along with a bearing block at the firewall and ditching the pump and hydro lines. This will add some needed room along with moving your battery to the boot.
As far as the A/C goes. You may be able to make your own custom lines to make it work with the 383.
Hope some of this helps you out.
Matt
