Replacing idler puller bearings K&T 2D bearing ID

My 2D is quite loud when running, I was afraid it might be the spindle bearings, but fortunately it isn't. It is the bearings on the idler pulley. My parts diagram says ND88026 and ND87026 on the bottom, but looking at the parts manual online it says 2 off New Departure 88026. I'm tempted to believe the online version, as the idler pulley looks more like mine.

Does anyone have a bearing cross reference catalogue that could give me a bearing number for a more current manufacturer? NDH88026

My local bearing supplier (UK) found the bearings, but wanted $100 a piece as they were "American". Found a pair of new old stock bearings in the US which have shipped to me. I removed the pulley using a homemade puller, and the old bearings are in a terrible state, so no wonder they were making some noise. In addition, the retaining lock nut, lock washer, washer and bearing spacer were missing. (parts 14,15,16 and 18 in the picture).


I have bought a replacement locknut and washers, but I am going to have to make the bearing spacer. I can measure the distance in the pulley between the shoulders that support the outside of the bearings using a depth mic, and I know the difference in width between the inside and outside races. My question is how long should the spacer be? If I make it the precise length measured then there will be no preload when I tighten the lock nut, and I understand it would be helpful to have some. So should it be a thou shorter, two thou, more, less???? The preload calculators published by the bearing manufacturers seem too complicated for my needs.

In case anyone wants to do this in future. The 88026 bearings are readily available in the US, not so much in the UK. The bearings are a light press fit in the pulley. I put the pulley in the oven and heated it up to 90C, 200F, both bearings just dropped in. I made a spacer (item 18) out of 32mm, 2mm wall thickness tube. My spacer was 2.598" long, which gave a couple of thou of preload when the nut was tightened down. The bearings were a sliding fit over the shaft after I cleaned the shaft up with fine scotchbrite. The lock washer (W05) and lock nut (N05) are fairly easily available. All back together now and running a lot quieter.

Here is a picture of the puller (you need a sleeve to go over the central part of the shaft that drives the adjuster).


Here is the shaft with the pulley removed, the adjustment block was missing a screw, added a new pair, 5/16 UNC x 3/4.


Here is the pulley back in place with the one of the new bearings and the washer, lock washer and lock nut,