We do not have a DC current probe that meets your 600A requirement. The closest we offer would be the TCP404XL. The TCP404XL is rated for 500A continuous or 750A non-continuous. The main constraint at these current levels is heat, as you mentioned. If depending on ambient temperature or length of your test, this probe might work OK for you at 600A. The specifications pertaining to this start on PDF p. 76 in the User Manual: https://www.tek.com/en/current-probe/current-probe-manual/tcpa300400--tcp300a400-series
As you can see from PDF p. 77, at an ambient temperature of 23 degrees C you can measure 600A continuously. However, there's some restrictions and warnings in this section (starting on p. 77) that I would recommend you cover thoroughly to make sure this will work for your test conditions. 600A continuous can be done but is right near the limit for this probe. Here's another helpful link: https://www.tek.com/en/datasheet/ac-dc-current-measurement-systems
