why buy new, when you can pay new prices for old stuff? http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=300043537456
See So-Cal Speed shop. http://www.est1946.com/index.asp?PageAction=VIEWCATS&Category=222 A little pricey!
A lot of new manifolds have the boss for the fill tube cast in. Just drill it out and put your tube in.
both edelbrock's Performer and Performer RPM has the boss that you can drill out. that is NEW ones , older Performers do not or you could check ebay for an old edelbrock C4B or C3B
Ragtop, if you don't want to drill out the oil fill boss yourself you can take it to a machine shop and they will cut it out for you. Take your oil fill tube with you so they can get a good tight fit.