For switching transistors, you can use IRFP4004, in transformer, maybe with the PM87 and like 10 copper foils in paralalel in two turns for primary, and 12 turns with litz wire on secondary would save a lot of space!
IRFP4004 has to low Vds value (40V). In the application, the input is 48V nominal, and up to 63V fully charged, thus 75V mosfet will be better. There is a lot of possibilities, for example IRFP2907ZPBF, IRFP3077PBF, ot this big monster (but expessive), IRFP4368PBF !!!
If it is possible to build this smps with only one transformer, I thought about this idea, and I think it will be easy to route the board, and build one transformer instead of two is better
But what size of core will be necessary for this 3000W 48V-->250V smps converter ?