I'd go for the Ego board. It eliminates the terrible upper board and requires less modification, while allowing break-beam eyes. You'll have to wire an Ego/DM solenoid connector to the Shocker noid, or use an 05/06 Ego Noid. There will be a little meat to take off the Ego trigger if you choose to use a Shocker noid.
1st- determine 05/06 ego noid or shocker/impulse/sport
2ed- desolder upper board, solder leads on noid, crimp, and take noid mounting screws to correct size
3rd- probably going to want to use ego board and eyes(oled screens are nice)
4th- (only if you use shocker noid) mill the top of the frame and back of the trigger to fit noid
5th- drill holes to mount frame to the body
6th- drill/mill body for break beam eyes.