can it be changed to be a 1050

Not really. It's in the flow of the main body. The work that would need to be done would cost more than a 1050. What's it going on? 1250 is good for 600cu in plus in under 6k apps.

going on a 540, what size do you recomend

540 calls for a 2 circuit 8896 1050 hp. HVH intake. I wld use two 2 in spacers.

i was thinking of 1050s since im also running brodix alum heads.

Yep that's a good combo. Bb2's.