The thermostat was optional in Anglers.
The cylinder head is exaclty the same of 6 hp, so it is easy to put it in place.
The correct prop is a 8" x 7.5" x 3 blades, left handle, and is essentially similar to the 3 hp one, with the same shear pin and rubber ogive.
I wondered the 5 hp can use a longer pitch than the 6 hp with the same gear ratio ( the 1976 and later 6hp uses 12:25 ratio and 8×7 prop instead of 15:26 and 8×71/4 of first series) but it is…
I have a ’66 johnson LD 11 and I will check if a part number is on its prop.