I’m going to echo what the others have already said..... get an Ed Brown. The Brown thumb safeties are probably the best there is. Although I feel they need to be trimmed a bit in length and width, once on the gun they are the most useable design, IMO. The pad geometry is optimal for most users and I have found that a well fit Brown TS is comfortable even for people who generally find the 1911 and the high thumb hold awkward. The lug design is also superior to other safeties I’ve used. When used with most hammers, once the Brown safety is engaged both the hammers forward and rearward movement becomes blocked by the engagement lug. Essentially the hammer is “locked” in position instead of just blocked by the lug. However, I’m not sure that is always the case with factory Kimber hammers and I’ve noticed that sometimes one must relieve the gap between the safety lug and table in order to get an optimum feel and ‘click’ when the safety is disengaged.... none the less the Ed Brown TS is the best on the market.
One thing to note, if you plan on using thin grips a Swenson-style ambi (like the Ed Brown) may not work. In that event the Kings ambi-safety that is retained by the hammer pin would be my next choice.