You need to read a bit more possibly.
You seem to be mixing up LPG running dryer than petrol.
The Morgan racers & others are running LPG not only for the weight benefit but also the Lower calorific value of LPG means its only 85% of petrol & actually runs cooler.
Plugs do get hotter tho.
My 4.7 is just fine because its built for LPG, & doesnt run petrol.
My 4.6 was also built suitable for running just gas.
I have 'flash lub' on my 5.2 tvr engine because it runs standard heads.
Never had a problem with it & its done lots of fast runs in several different vehicles.
No valve recession
or other such problems you have maybe been told about.
I think i have covered enough miles in LPG vehicles to be satisfied that it works for me.
Then i just do like NIKE says,
this seems to work just fine.
george