http://www.northernclassictrucks.com/ Not sure how custom you're talking but these guys seem to make a lot of nice pieces.
About any bed that will fit between the wheels cn be adapted, just try to keep the fenders original or at least similar in style to the front ones... Think about fitting something like '37-'39 Ford car headlights into the front fenders instead of those "alien apendages".
That's why I am building my '41 without fenders, and with a '39 Plymouth car grille shell...I will use low-mounted Ford commercial lights.