Not an ironhead, but on my 74" pan I'm running a 46 low and a 185 main, stock needle. The XL needle was made to compensate for the lack of an accelerator pump on the older CV's, so it's a bit richer through the midrange. Pro'ly not needed for yours, but it's something to think about. If I were you, I'd start with a 45 low and 180 main, stock needle shimed up a slight bit. Your most likely problem, if you have one at all, will be a lean cough off idle, or a slight bog in the mid-range. If the former, go up one size on the low, probably a 46'll do you right. If the later, go up one more spacer on the needle, or use the XL needle. In the unlikely event that you're running lean at WOT, then up to a 185 you go...

-Kuda
'49 panchop

 

I use Yost kits on most cv carbs.... 175 main and 45 slow......You need to drill the slide to accept the new needle...make sure your shims are under the clips ....if it has a hard time idling go up to 46 slow......good luck

 

74-inch FLH, stock "H" cam, 2:1 headers into baffeled cigar muffler, points ignition, I run 2.5 turns out on the idle mix screw, 52 pilot jet, 190 main jet, stock needle with no shims, no mods to the slide.

Starts easy, accelerates smoothly with no flat spots or surging, nice clean plugs. I tried the XL needle but the throttle response was crisper with the stock needle. Most common ranges are 2-2.5 turns, 48-52 pilot, 175-190 main. You'll probably end up in the low to mid area of those ranges. Great carb!