Paul, it should be as simple as swapping your 3/4" bearings for 25mm ones, they are the same OD. You can buy bearing kits from your local friendly dealer, which come with bearings plus the correct internal spacer tube. The one caution I make is that the central hole through each hub may need to be bored, to provide clearance for the larger spacer tube. I have a similar year rear wheel in my Glide and converted that from 3/4" to 1" and had to bore it.
Thanks Grbrown That is what I thought after digging around some more, Im not sure Ill need to do machine work from what I have been reading. Now finding the right tires. I would like to put a 180/16 on the rear but most say 150/16. More reading.
How wide is that rear rim, measured inside the raised edges? If it's 3" then a 150/60 is indeed the widest that is recommended, 150mm being 6". Check the website of your preferred tyre brand.