You don't need a pump.
Go to the Firestone or Goodyear web site to find your tire's capacity, they list just about all ag and industrial tire sizes as gallons to 75% level.
Get the tire adapter, review grade school subject "siphon", get valve to 12 o'clock, take weight off tire, remove valve stem, insert adapter, set up a 55 gallon drum in the loader bucket with your mixture, raise high enough to start siphon, start siphon.
If it turns out that you want/need more than 55 gallons figure a way to replenish the barrel when it is say 1/2 way empty.
Once the siphon is started you probably don't want to break it, so better to top up the barrel than to start over.
I have never had to use more than 65 gallons, YMMV.
R4s for some compact tractors take as much as 50% more thanR1s for same tractor, they're just "FATTER", turfs are similarly "FAT".
It may or may not be the best decision to go for a full 75% fill, see whole treatises on
ballast, traction and efficiency - your choice, but there IS such as thing as too much ballast.
Once it starts, MAYBE raise the bucket all the way, if you are confident that you won't dump it back onto yourself (-:
Tie it in if you are a reasonably cautious person (I am).
Leave it, go do something else, like the watched pot that never boils, this takes FOREVER if you watch and wait.
PS tie something to the end of your siphon hose to make sure it stays on/near the bottom of the barrel.
Also, make sure the bottom of the barrel is always above your tire valve.
As I said, review grade school subject: "siphon" (-:
{I will re-word that for the purists; make sure the level of fluid in the barrel is always above the level of the valve (-: }
==============================================
Once you have done this you MIGHT want to review your general driving habits, particularly with regard to FEL use.
The initial impression can be that the tractor now REALLY STICKS TO THE GROUND - and it does.
There is some risk that you may be tempted to "do more", e.g. try cutting more aggressively with the bucket.
Well, it still ain't a dozer. The FEL is still just the FEL.
Rear wheel spin has been your friend, your "force fuse", it has protected the FEL and you.
To continue the analogy; You will be replacing a 20 amp fuse with 1/4 inch bolt.