I have an oil pump that I believe will work on your 5.0. It's a Melling pump part# M-68. I bought it for an '86 F150 that I had with the injected 5.0. I'm almost positive yours takes the same pump. I'll let you have it for $5 just because I don't really need it anymore.
I did a little searching to make sure it would fit. I found this page
http://www.cantonracingproducts.com/...lling.html#sbf
About half way down the page it has:
289-302 FORD OIL PUMPS
#M-68
289-302 Ford Standard Volume