We usually drill a hole in the side of the pan and weld a block of aluminium drilled and tapped for the truck style dipstick or just weld a block and tap it for a 90 degree fitting with a pipe thread on one side and a compression thread on the other.Use a tube and compression fitting correct for the tubing.Putting the dipstick below the windage tray or screen will keep it away from the rotating parts.Another esay way is weld a thick block and thread it to accept a site glass similar to what is used on hydraulic tanks on heavy equipment.The ones that have a round 1" glass face is easy to see and cheap