Arch I don't know the answer to your question, and don't spend enough time with Task Force trucks to know the ins and outs. But I'd suggest you can either use a 235 pan and oil pickup, or modify the pan and the oil pickup on the 261 if needed to make it fit.
Maybe someone knows different, but unless someone else has tried it you may be on your own figuring this one out.
I'm currently putting a Cadillac 500 in a '54 GMC and since not many have done it, finding answers based on experience is a little tough...
