Lovely rifle you have put together there; even the scope matches the style and era.
Value of a Venom is in the whole package. What it looks like, how it shoots, and does it feel its had custom work done. There is little financial advantage in not telling the truth on the history of a rifle. A modern custom tuned rifle demands the same premium and worth is how nice the rifle is. In real terms what was paid for the work is barely ever returned, at best you get the money back. The return is owning and enjoying the rifle for a while, and that is priceless.