Advice for especially altimeter is get TSO stuff, Yellow tag (ie fixed and calibrated) ex US is less than than non TSO and will last longer and be fixable.
In my case, non TSO altimeter packed up after ~200 hrs so old altimeter (smiths probably pre TSO) cost a slab, maintenance (ie cleaning to deal with stuck setting) and VFR calibration cost $160. Didn't fit as knob in wrong place (not the first time I've had that problem !) didn't want to hack the panel so swapped with an Auster guy for a United with 3 month old calibration certificate
Talking to the instrument guys at MB they were told by CASA not to calibrate the (insert well known non TSO brand) altimeters.
Edited to add - Radios are a nightmare get an Icom VHF panel job not one of the things that fit in a 3 1/8 hole.