I'm building a 4 star 60 (arf) and am putting a YS63 in it. The problem am having is that the instruction don't say how far out the motor should sit out from the firewall. And that the engine mounts that came with the kit, the throttle linkage won't clear. Also the high idle needle valve hits the side of the fuselage. Is there a different mount I can use? Any tips would be appreciated.

If it's like the 4*40 I'm building now, the instructions say to mount the engine so the prop clears the cheeks. You can move it more forward if you think you might need more weight forward.

I cut some of the plastic brace away to give clearance for the throttle cable. Shouldn't hurt the strength of the mount much.

It's common to have to cut clearance for mufflers and needle valves. You might be able to just cut a hole so that the needle valve sticks out. You may have to remove the needle and install it after the engine is mounted.

on my 4*40 I used a Dave Brown mt - the back is round - turned it so the cylinder is @ 10 o'clock& cowled it with balsa.
I suggest u get to to where u can get some idea of the planes balance point before u drill for the engine u can make up a lot
w/1/4" or so & its not noticeable.