I use heel toe, yes. Well, because my manual cars are 90’s Japanese imports, I use one side of my foot for the brake, and the other side for the throttle. The pedals are too close together, and the throttle is too short, for the proper heel-toe posture. 
Lots of car mag articles would comment on whether the brake an gas pedals were correctly located for good H&T. Not that it mattered to me…
Most manual cars I’ve owned needed the gas pedal moved a bit for proper heel and toe. Slop in the bolt holes or slightly enlarging the bolt holes fixes that. Pedals too close can result in “unintended acceleration” complaints and lawsuits so manufacturers have moved them apart over the years.
Slightly off topic… BUT getting back to the synchros:
My 1979 Toyota Celica (W50 tranny) has brass synchros, as do several other 5 speeds.
Just how important is it to use GL4 gear oil as opposed to GL5?. The FSM recommends GL4 80w90. I have a pail of this from a mail order petrol co for like the last 10 years. I have enough left for 4 more tranny oil changes, and by then I may be pushing up daisies.80w90 GL4 is hard to come by today.
I’ve heard that the sulfur in GL5 attacks the brass synchros (at least it’s mentioned) if one Googles this.