BB for SB...Your opinions please.

I picked up a 78 440 out of a Dodge truck...127k miles, running great. Motor is pretty clean and ran on propane its entire life. Given the pricing for headers, oil pan, linkages, cooling, trans, etc., I was thinking of ditching the BB idea and possibly finding someone to trade a decent SB for the 440. O really want the 67 Valiant on the road this coming spring. There is no way my budget will allow the BB. I really wanted it that way but driving the car is more important at this point and I can upgrade maybe next winter. So do you think I should try to swap? Is my 440 of enough value to get a decent ready-to-go SB in trade?