Dr Diff sells billet steel housing ends here:
http://www.doctordiff.com/billet-steel-housing-ends.html
BUT, you can't, or should I say shouldn't, just weld them on. Getting them on square is most crucial.
You should really have these:
http://www.ebay.com/itm/321209787507?_trksid=p2060778.m1438.l2649&ssPageName=STRK:MEBIDX:IT
And a steel rod that slips through the entire length of the housing and through those fixtures to properly align the ends.