I have also done one of these conversions. As others have done, I used the existing tender axles but with Alan Gibson wheels. I used a new 2mm axle for the pony wheels but kept the Dapol spacer and put it on the new axle. I also used the available bushes for 1/8″ to 2mm on the driving axles. I used the Alan Gibson ones and they were fine. I found that 1.5mm of spacing washers either side were necessary on the front and rear drivers while 1mm was enough on the centre axle. You need them on the rear axle otherwise the crank pin nuts can hit the fairing under the front of the cab. The Dapol crankpins are 1.5 mm so Alan Gibson crankpins fit the existing coupling rods and connecting rod, though I left out the very thick washer that Dapol put between them. The existing pickups worked fine with just a bit of a tweak. You just need to be careful that the two wires to the Dapol pickup strip pass either side of the square block below the leading end of the keeper plate. Otherwise they get caught between and cause trouble.