If everything is clean, the head is within spec for flat, the cylinder liners are all seated fully, it should not need sealer.
If you do use a sealer, be very sparing with it. Especially around the oil passage hole at the back. Plug that hole and no oil to the rockers! I used to use aluminum spray paint, seemed to work good as anything without squeezing out and blocking ports.
A retorque and second valve adjustment should be done after the first start up and brought up to operating temp.
You can temporary a "nurse bottle" to the carb from a quart oil bottle with a pointy cap and a piece of fuel line.