Do you have a Thor or GEMS? It makes a difference to where some people put the ECU and the injectors.
I DIY installed mine on a 4.6 GEMS. Rough positions are...
Gas ECU inside the car! On top of the ABS ECU under the glove box. Keeps it clean and dry. Owners of Thor engines often use the old engine ECU box behind the battery.
Gas level switch/level display in the cubby hole next to the clock.
Gas vaporiser to the left of the EAS box. Some people put it on the other side next to the brake system, but I didn't think there was much room.
Injectors are best put in twos on each corner of the plenum on a GEMS. Then connecdt up with hose to make a fuel rail. Thor I've no idea I'm afraid I haven't seen one close up.
You'll need to drill and tap holes for the gas nozzles as close to the petrol injectors as possible, plus a couple more for pressure sensors and vacuum advance (depending on the system you install).
Tank in the spare wheel well. I bought a bracket and attached my filler to the underside of my bumper (I have no tow bar). This means I avoid putting a whole in my bodywork. If you do have a tow bar I'd consider attaching your filler to that.
Tank needs bolting down securely. You need to use washers that are 50mm dia and at least 3mm thick to meet regs.
If your tank doesn't have mounting brackets on the bottom, either get a tank that does, or you'll have to fabricate some box section welded to the chassis rails to hang your tank. You might be able to buy a bracket that will secure your tank to the floor of your wheel well instead. I'm not sure.
Make larger holes to feed the inlet and outlet pipes through the back of the wheel well, so they come out just below and behind the bumper. A loop must be put in the pipes here to protect in case of rear impact.
I suggest buying rubber gas pipe instead of the copper stuff. It's more expensive, but oh so much easier to route under the car and to the filler. I clipped (metal not cable ties) my pipe up every 300mm which is better than the regs ask for, but better safe than sorry. Also, you can't go within 150mm (I think) of an exhaust pipe without fitting a heat shield between the exhaust pipe and the fuel pipe. This can be tricky with a V8 with two exhausts! Mine follows the line of the air suspension pipes along the chassis rail using the chassis rail as the heat shield.
There are also loads of clips, clamps, grommets and electrical connections that need making. It's easy to do when you have a kit, but when you don't know what you have and haven't got it could be cheaper to get a professional involved.
You could buy a kit and just take the injectors, gas ECU, tank and valve off the shopping list and then you know you'll have most of the bits you do need.
Finally the whole thing need certificating by a professional and adding to the LPGA database. There are loads around that will do it for you, costs about £60-£100, but if you've got something wrong or non compliant they'll fail it, so you have to take it away, mend it, then submit to the test again.
It might be cheaper in the long run to buy a kit because it will come with instructions that tell you exactly how to fit it. There will be no mistakes, and so you'll on the road sooner and reliably.
Tinley Tech and
Blaze Autogas have loads of parts and excellent advice. Blaze are Land Rover nuts and sell a kit specifically for the P38. They might be worth a call.
I submitted a 'how to' for this site when I did mine, but it's never been put up!
Also have a look here..
http://www.blazegas.com/kits2b.html
and here..
http://www.cowdery.org.uk/rrlpg.php
