Bolt is 3/8" Whitworth.

My 15J ran with the vacuum pump port blocked for years with it blocked it cannot suck air in so does not pressurise the sump.

Is the firing order right have not had any experience of V8 but two of the adjacent leads look to go to left side of pic would have expected them to alternate.

Try changing to the 7:1 spark plugs to see if it changes anything. How are you timing the engine? Personally I would be slackening the distributor calmp and giving it a tweak to find the sweet spot wher it will run smoothly. Book figures are not truely relevant now with modern fuels.

larger studs should be diagonally opposite each other was an attempt by Rover to reduce the movement of the arm on the swivel when stressed. Page 4 in attached pdf referes to the larger studs when changing position of arm Page 2 in 2nd attachement also mentions different nuts

two snips added 1 series 3 1 from series 2 parts book which matches your pic If you do a web search for Smithies landrover it will bring up a NZ website where you can download all the parts catalogue and some other information a useful resource.

Remote servo will fit in the space under drivers side wing to the right of your current brake pedal. non of the 200tdi parts would normally be located there.

You do not need a vac tank easiest option is to fit a later servo version pedal box or you can use a remote servo. Which will fit under the wing on the offside.

Have you tried it with the clutch depressed.

AP landrover on ebay where selling Santana versions I bought one and fitted Currently they are selling some made in Italy may be worth a punt aty that price. https://www.ebay.co.uk/itm/401127447532?hash=item5d650f1bec:g:5nUAAOSw7H1ZlW3J

Wheel bearing numbers in the attached doc do a search using the bearing number.

The axles themselves may still have a visible number stamped on axle case rear passenger side /top. Can you find the rear diff number to see if same ball park number. Late 1980 had different half shafts and two same size bearings in the wheel hubs.

Where is the VIn plate fitted? Maybe that part has been replaced. Is the VIN number on the V5 and does it match?

Sounds like you have a ringer no way the chassis can be legally shortened. so some pics of chassis as 88 and 109 are made differently. 88 4 plates welded together 109 two halves welded to gether with seam top and bottom.

After market relays often have smaller diameter at base there is a seller on ebay making a smaller lower clamp ring to compensate for this sure it has been on a recent thread on here. This guy has one of a specific size...

Mainly meant for use with a winch or other static equipment ie power takeoff / generator etc.. Optional parts catalogue shows all the parts

You will need a military parts book as well as sensor may be a different part to civvy version. Blanchards list a different gauge for military https://pablanchard.co.uk/Gauge-Oil-Temp-Eng-IIA-Military-500555. Give Blanchards a call they may be able to advise.

I was under the impression Military vehicles had a different type of gauge and do not need voltage stabiliser. Have you a wiring diagram for the FFR

I think it is 1/4" BSPT. https://www.ebay.co.uk/itm/232606369920?hash=item36286b8880:g:0LIAAOSwyi9aPi2W Engine would have had a bracket that the plug screwed into for storage when removed from housing have a a look in case it is there. in the same vicinity.

Is the internal diameter of the seal not a good enough guide? I have some of them dimensions in the attached pdf. The handbrake speedi sleeve inner and outer diameter is also there. Bottom of page 12 top of page 13 your pdf seems to be the choices