I have seen one of these lenses, a convertible lens.
Are these lenses in a #3 shutter. I was thinking this lens wont fit on a Pacemaker Graphic.

I don't see any reason why it wouldn't fit just fine. I don't have that lens but I have a No. 3 Ilex shutter and it would fit.

I have used #3 on my graphics before with not problems, it should fit just fine, heck I even tried a #4 Ilex with a 254mm and was able to make it work, not easily, but did get it to work.

Dave

I have one in a Compur shutter but have no idea what number it may be. It's also mounted on a 4 inch board for use on my Views...

But the flange only measures less than 2 3/4 inches and the rear element 2 1/2, so it should fit into a Pacemake with no problems...

You won't be able to use it converted though. That 420mm needs better than 16 1/2 inches of bellows for an infinity focus!