Technical Trans swap: making a driveshaft

I have a Ford 3.03 3-speed trans and a Borg T18 4 speed trans. The 3.03 has been OK behind this +0.30 390 FE for a while, but the engine has been updated on the top end to make 400+ hp and lots of torque. The 3.03 also has a narrow dogleg 2nd shift pattern, which .. sucks. Straight back from 1st gear is Reverse, and you can imagine what a missed shift would do. Actually looking at the dogs on reverse, it looks like the old 3.03 suffered from a lot of missed shifts and bad clutch adjustment for a while..
I got the T18 to add a little strength over the 3.03, plus the 3 is probably in need of a rebuild.
The T18 came with a tail shaft housing and fixed yoke that looks like it had a transfer case behind it (probably Jeep). The extension housing on the T18 is 2" shorter than the 3.03, and of course there's the fixed yoke problem.. I haven't pulled apart the T18, so I'm wondering if I can make the T18 a slip yoke and then make a driveshaft the right size, or see if the current shaft is long enough, or move the rear end forward a few inches which I kinda want to do anyhow...
Mostly the problem at this point is fixed yoke vs slip yoke. Can a fixed yoke ext. housing take a slip yoke on the tailshaft? Much thanks,
Brian

 

If it won't I would consider a drive shaft out of a 4x4, maybe a long bed, with a slip yoke on it. Bolt up.

 

I am going to say not to the slip yoke. Just got to a wrecking yard and get yourself a jeep style driveshaft with a slip joint on it and build your driveshaft from that.

If you need a long driveshaft an '84 3/4 ton suburban has a slip joint.