its time for a valve job and springs and i was thinking about upgrading the cams.what could i use without getting into porting and pistons dont want a complete taredown yet.

crane 741 or merc 525efi cam specs also a crane, both are very similar. shave the heads a little to raise your compression. they say you can do the 4 7 firing order swap for another 10 to 30 horse it all adds up.
cam specs were .610 .632 on both
I think dur. 234 242 112, efi 236 244 114lobe sep

525EFi cam is Crane 741 on a 114 lob sep. Normally the 741 is on a 112. The 525EFI will give a little smoother idle. Its a good choice.

This can happen with a 502mpi with the a 741 cam??? There will be no issues with the ECM??

You said HP500 not 500EFI. You will need to modify the ECM fro any cam change on a 500EFI. I don't think the 4/7 swap can be done with the EFI.

I did all the modifications needed when I changed the cam, but since I read that 4/7 swap can get from 10/30 hp, I thought of trying it. but it seems that it works only with a carb engine.

I'm pretty sure it will work on the efi also. swap/ change the injector harness. On second thought doesn't the mpi ecm fire all injectors on compression strokes?

the motors are carbed called on the 741 cam was told i have to run a longer lifter with that cam. lifters are 600.00$$$$.

All 500hp engines run the correct Crane lifters. However, if you are doing a valve job, it's time to change the lifters anyway. Sorry