L2550 tires

I am new to the tractor world, after some google searching i stumbled across this site which seems to have some great info... I recently picked up a L2550 which has 212/80 D15 front turf tires and 355/80 D20 rear turf tires that hold air for now but are very cracked and aged.. The tractor will be used primarily to maintain hunting property and used around the yard. I am leaning towards replacing turf tires with R4 or R1 tires. I assume the R4 or R1 tires would require different wheels then the ones i currently have with the turf tires. Looking at the owners manual it shows front rim size of 7-16 and rear 11.2-24, the tractors is 4WD..Can anyone shed some light on this??? Best place to find wheels? What's on your 2550? Thanks in advance