JB, your car and my car are from roughly the same time period. I am 2291 you are 2218. Both of our cars use a rear axle that was sourced from Dana Australia. The Australian Dana is not the same as a Dana 44. It uses different everything including gears and probably half shafts although I don't know about the half shafts for certain.
If you send your half shafts to the Driveshaft Shop they might be able to duplicate them. I don't know if US axle splines and Australian splines are the same. If they are not different you could likely get lucky and have a pair of their half shafts fit nicely.
BTW Australian Dana parts come at a premium. I was looking to change my final drive ration and the price was $600 for a ring & pinion and the icing on the cake is the ratio choices were very limited (three at the time if I remember correctly) and none were close to where I wanted. Extra added attraction is the $600 price does not include shipping or import fees both of which give the number a nice boost upwards.
I am in the process of converting over to a Ford 8.8" aluminum IRS center like Ford has used on so many of their daily drivers. The strongest of these centers is the one they used in the 2007 to about 2010 Explorers. Here is a link to a post that I talked about the rear ends in and posted some pics also, click here =>
Ford 8.8
The pic below illustrates the Explorer center on the left and a 03/04 Cobra unit on the right.
The Explorer IRS center section is the strongest aluminum version of the 8.8 that Ford has offered. The Cobra version is the same as all the production passenger car versions. You should be able to find an IRS center section in the salvage yards fairly cheap. If Ford is still selling them the price should come in around $300 to $400 (sorry I forgot what I paid) for a brand new unit.
You would be wise to put as much distance as you can between yourself and that Australian Dana. The center is not bad, it is just difficult and expensive to maintain, parts are generally not available — and it's probably not as strong as the Explorer alternative.
Ed
p.s. you'll need a chassis shop to do some fabrication to install it for your generation of SPF.