The Exmo front suspension was always Sierra track control arms, sierra ARB and sierra steering rack with sierra uprights. It used custom struts of unknown origin with Robin Hood adjustable spring seats.
At the back there was the option of standard sierra rear springs and shock OR an adjustable RM adapted mini rear shock modified to coil over.
Further to the fuel sender.
The top of the tank can be reached by removing the boot lining. How to line the boot was left to the imagination of the builder so every one will be different.
Alternator light on no charge = dead alternator most probably brushes and slip rings oxidized due to long lay up.
If made with cut down sierra dash (instruments showing in dash between seats) then also oxidization of multi plug a possibility. Try squirting switch cleaner over contacts whilst connecting and disconnecting plug several times.
Fuel tank is across back of car. Filler is on right side into top and sender is on left hand side also on top. To get at drop tank. Be careful removing sender as resealing can be hard. Filler is cut down sierra into standard sierra rubber gasket/sealing ring.
Where are you?
Vacuum advance is mostly an economy system.
At full power it does nothing as there is no vacuum in the inlet manifold with the throttle fully open.
As you close the throttle inlet vacuum increases and the fuel/air charge entering the cylinder reduces. This reduces the pressure in the cylinder at the end of the compression stroke. The flame front of the burning fuel/air moves faster with high pressure and slower with low pressure so ignition advance curves attempt to get full burn happening at or soon after TDC to extract maximum power. If full burn comes later then engine efficiency falls.
A couple of thoughts.
1 oil level a bit high or windage plate missing in the sump leading to frothing of the oil so there is air in the oil and this limits oil pump as it is now pumping oil and air. Have you got the standard sump or has it been modified?
2 oil not draining back to the sump and sitting on top of the cylinder head. take cover off and check that drain holes are clear.
Rust in the head.
How far can in can you push a 7mm drill? Is it far enough to take the new sender?
If so you could use a 8mm drill bit turned by hand to clear the *bleep* out.
One front wheel locking before the other can be due to corner weight problems.
The spring platforms are I assume adjustable.
It can be that one diagonal takes more weight than the other diagonal so the weight on each front wheel is different.