I have a good condition M1917 Enfield rifle in .30-06 Springfield that I inherited. It is not actually a Lee Enfield, which I have used as a teen to hunt deer and we referred to it as a .303 British.
During WWI we actually produced more 1917 Enfields than 1903 Sprinfields.
The 1917 Enfield was simply a British Pattern 14 Enfield redesigned to handle the 30-06 cartridge. The pattern 14 was actually a Mauser action which the British had intended to replace the old SMLE with. It was also going to be a .280 caliber.
When WWI came along they abandoned the .280 since having two different cartridges would have been a logistical problem. They contracted with American manufacturers to make pattern 14 Enfields in .303. I am not sure how many were actually made but I once had a pattern 14 in .303.