1.8 crower rockers on a magnum head ?

So I have used 1.5 1.6 and 1.7 SBC rockers on magnum heads but am wanting to try a set of the 1.8 crowers, my only concern with just buying a set is it says ".050 backset trunion" ... what the heck does that mean? Am I going to have to re-drill the bolt holes .050 back from the valve? I could and upgrade to 3/8th studs but there is not a lot of meat in the pedastal for that... any thoughts?

PS I do not want to get into the argument of "why" as I see several good reasons to do this and have had great luck with higher ratios and wish more stuff was available for small block mopars.

And in case anyone wants to see them

http://www.summitracing.com/parts/cro-73695-16/overview/make/chevrolet

The Rockers are moved back .050 from the valve to run longer valves .100 longer.

The trunion is the pivot bearing in the rocker. The bearing assembly is offset where the hole comes through for the stud. That's all that means. You don't have to do anything except put them in with the offset in the right position.