The MII conversion is mainly useful for installing physically large engines. Unless a lot of bracing is done, you end up with structural problems. Dynacorn has a shock tower with relief, allows using MII or coilover suspension without eliminating the export brace.
Of course, the MII suspension is not a serious upgrade from the stock 64-70 suspension. It was mentioned that TCI's MII was better than stock. Well, duh. You put upgrade stuff like that on a "stock" suspension, tubular upper arms, roller shafts and perches, etc., you get the same result without hacking and welding.
Doing this conversion to get PS and PDB is not very cost effective. Stock 67 discs are superior to MII brakes. You can get them for under $600, and bolt them on between dinner and bedtime.
If you find Ford/Bendix PS offensive (I don't, I've worked on this stuff a LOT, and 99% of problems with it are dumbass repairs) there's always the Borgeson kit, and several R&P kits that are bolt-in for 64-70.