You can get factory workshop and other manuals here: https://classic-motorbikes.net/manuals/
I agree. This is very important on an A65. You need to measure the crank journal and the bushing to determine if its still in tolerance. If not, you need to have someone who knows this process do the machine work. It must be line bored so it is concentric with the bearing in the left hand case. Morrie's Place in Ringwood, Illinois is a good shop that knows how to do this.
SRM sell a tapered bearing kit. Have a look at the swingarm bushings as well, you didn't say what year it is, may have silentbloc bushes. There are better options that require machine work depending on how far you want to go, I converted mine to oilite bronze bushings
How can you fit needle or roller bearings to the oil feed bushing? I once threw a rod through the case of my A65 due to not checking the clearance when I changed the crankshaft.Too much clearance in the bushing will reduce oil pressure. I can't imagine how a needle bearing would impact the oil feed to the crankshaft.
Plenty of people do this conversion
You can see pics of the conversion in my A65 build thread here:
2 diff frames were used, what year bike? last 2 yrs 71-2 are known as oif - oil in frame, same as triumph used with t120 - t140 models but with diff engine mounting locations fitted
