Decide how you want the back springs to be mounted, or rather how permanent of a conversion you want it to be and get Thunderbird equipment. Tokico offers 1.25" drop. Vogtland offers 0.75" drop or 1.6" drop. Eibach offers 1.5" drop. Sprint/ST/Spring Techniques-Tech offers 2" drop. As far as upper mounting brackets you can use perches cut off of the upper body of a Thunderbird and weld them to the body of the mark, they are direct fit, you could buy the upper plates from one of the mark VIII kits, you could buy those fancy perches from DLF, you could use snowflake center caps bolted onto the body, or you could make your own. Then you just need front thunderbird/cougar/mark VIII upper shock mounts, thunderbird/cougar shocks-struts, and either new mark VIII rear shocks, reuse you existing ones, or use t-bird ones with the proper mount.