You need to get shorter inserts and shorten strut tube to suit, unless you plan on running stock ride height, the stanza struts are longer than the stock 1200 struts but they do have a lower spring seat that will fit in the 1200 strut tower. I would steer clear of stanza struts and get an already short strut (with better brakes too) and just cut and weld your lower spring seat on from 1200 or 120y strut.

My daily has Mr30 struts, racecar build has 280zx struts, and my partners car has stanza struts shortened for Z31 inserts.

To convert the front end to run any of the larger strut sizes ie. 1600, 180b, 200b stanza, sunny etc. You need to use either Sunny or stanza lcas, steering arms (R31 and MR30 need a sheer load spacer between steering arm and strut, datsport sell these), balljoints, and outer tie rod ends. Then you need late model 120y radius rods to get a decent amount of castor otherwise you may find the wheel hitting the floorpan. Use your 1200 strut tops, bearings and top spring seat, brake lines and then upgrade the master cyl, I don't like boosters.