old ?
As for range on lpg only, my 80 litre useable tank should go some distance , lately been doing about 62 l 540 km - used to be 70 l for same distance - the fuel seems to change ??? So, should be able to do 600km without pushing the vehicle , but, not with full payload area
Ring mixers work OK on postive pressure systems that the euros seem to make, Impco has always been negative pressure until lately they have a little positive pressure Cobra for jamming a ring mixer in somewhere.
I was always hesitant about conversions that needed to be thought out and custom built as opposed to the pre assembled kits that arrived in a box with every nut bolt and screw needed to have the thing up and running.
The hesitation was uncalled for each time.
If you go dual fuel with a petrol carby you really need to adopt a running method such as start and finish each day running on petrol so the carby gaskets don't dry out or things gunk up from being dry. Pick a point a few kms from home that you switch to and from petrol, so it arrives home at night with a bowl of fuel for next days start on petrol.