You have a lot of shim under the rocker blocks.

It probably has lash caps or some swivel foot adjusters in there causing the need for shims. Which also would mean custom length push rods.

It used to be common to do it this way. Now a days it is considered better to back cut the rockers so they do not have to shim so high.

This looks like it could have began life as a CB perf kit or turn key engine. I see the dune buggy sled tins and such and it makes me think it was a competent engine builder.

Even if those heads are "as cast" they are far far from stock and are not for a stock displacement engine. I would agree that it possibly is somewhere around the 1800 to 2000cc range.

This also puts it right in the best size for dual 44 idf weber carbs.

Dual 44 webers on a 1800cc engine will have tiny low speed jets. The smallest piece of trash plugs them up. Dust/dirt from poor filters, fiber from a fuel filter disintegrating, rotten fuel lines.....all will plug one up quick.

Assuming the dual webers were correct to begin would be a lot easier to repair them than it would be to re-do all the custom tuning all over again.

You really need to find someone near you that knows some VW.