Back in "the good old days" (I was there! where were they??) before sub kits and ready made crossmembers.We used to use cut up Pinto-Must II etc. stock front crossmembers. Untill you get into these you don't really realize how CHEAP and flimsy the stock pieces are!! Fords idea of re-inforcement is to spot weld multi sheets of body sheetmetal together and rely on the unit body construction to hold everything somewhat together.
When you trim this unit from the donor car you are removing all this (bracing?!!) and then you have to grind away even more metal to get the thing to look like something. Plus you have to cut holes in it to position it on the new frame. Every cut makes this thing more flexi and eventually you have to start adding bracing ( adapting 1/8" plate to four layers of spot welded sheet metal is fun) and figure in your front end alignment specs (anti-dive etc). Thats why the kits are more time and safety efficient. That "few hours of cutting and grinding" starts to become days.Compare, even the cheapest kits use 3/16 ths thick crossmember material and the front end specs are already done for you. I used to make my own for the odd ball stuff I did, out of 2x4 and 2x6 box tubing. But you need a chassis jig to get it right. Example= Big block Chevy in 59 Ford Escort 100E, Small block chevy in a 58 Triumph 10, Big block Chevy in 60 Studie Lark, Small block Chevy in 36 Hudson Terraplane, 28? Essex Coupe. But now Fat Man even has kits for some of these! Who woulda thunk it!!!.