ORIGINAL: Hilux
You dont need a heater, although in my personal opinion itd be a folly to remove/disconnect it, unless you have to seal the bulkhead. Even then a race car will still have it in order to demist on a wet day. A road car must have a demisting device, as stated above.
So true, have you ever done a cold wet track day with no heater/demister?? Alternative is an electric fan heater designed for the purpose, small, light and removeable on hot days.
I've already removed the standard belts and just fitted E(4) 4-point harness with seatbelt type buckle..used standard mounting points for both, front and rear..the harness i used came out from my '86 Alpine White..although personally i didn't think it was fitted up to standard and rather unsafe (front point were mounted onto bolts that were welded onto the sides of base frame/sliders not chassis!!?!, rear points were joined and bolted through floor using just a bolt and nut!!) it still passed MOT..[:'(]
Unless you need to use them for a very good reason then try and avoid the 4 point belt buckle types. They are cheap but you get what you pay. You also cant get out of them when upside down!! Use a quick release type harness where all straps release and 3" shoulder straps which spread the load better. For an MOT simply bolt in the old seatbelts - its 15 mins work once a year.