Car Craft is a magazine dedicated to selling parts, keep that in mind any time they write an article.
Here's how to bolt a muncie onto a 5.3L using only stock parts.
For the TH 350 you'll need a spacer for the flex plate, it's like $40.
No extra 5 bajillion dollar conversion cost.
Most "hotrodders" today can't build anything unless its been approved by a magazine editor and delivered by the UPS guy- that's not building, that's buying.