VH Commodore Questions

Hi group,
I've just brought an 82' model VH with a 202 reco engine which has been 
converted to gas.
It has apparently been properly modified to run on gas, cannot use petrol 
now they tell me.
Is there any special oil I should be using?

Also, this car has been fitted with an after market s****ts steering wheel 
and is causing the horn to go off when selecting the left indicator and 
turning left.
I dont yet have the manual for this car so I dont have the wiring diagram 
yet.
Any suggestions as to where to look for the horn prob?

Another one, the auto transmission slips when starting in drive mainly 
between 2nd & 3rd, the way around this has been to start in 2nd and when
it 
gets near 60k's changing back to drive minimizises the prob.

Is this gearbox screwed or is there some adjustment I can do?

Cheers
Mark