check out gmc paul. they sell a 63-70 drop spindle that will use the original ball joint etc. , but you have to switch to the disck brake upgrade.
http://gmcpauls.com/Suspension.htm
IIRC, I looked at the LMC catalog and the upper and lower control arms were the same part # for 67-72, just the balljoints/tie rods etc. are different
we did the complete front xmember swap and rear swap from a '72 to my son's '67, if you go this route get everything suspension/brake related and it will save you alot of time.