ringet421, welcome to HuntingNut. There is some limited load data for the .243 with 75gr bullets.
when I'm using a powder without published load data, I use published load data with similar powders and ratio the loads to the powder-bullet combination I want to develop. Example, 80gr .243 uses 36.0 grains of Varget and 44.0 of Superform and are published minimums from Hodgdon. I then use this ratio for .308 Varget loads to determine a starting min load with Superformance. If you use this technique, do so at your own risk. It made me feel like I reduced mine. It definitely takes longer to develop your own load data this way. Published data is nice to have. Let us know what you find out.