There is no reason you can't convert the 235 to a closed crankcase, PCV, system. You could modify the road draft tube on the right side of the block to take a breather style cap that has a PCV in the center of it and use a conventional breather up on the front of the valve cover, or put a breather on the modified road draft tube and use the PCV type cap on the valve cover.
Ford used the PCV in the oil breather cap in the late 60's and early 70's as did other car makers and the aftermarket offers them as well in chrome.
For the exact PCV valve I'd suggest using one for the later 230 - 250 Chevy sixes. You can connect the hose to the engine on an unused intake manifold fitting or tee it with an existing vacuum fitting of adequate size. Your idle will be slightly effected and will require some minor carb adjustments due to the added air introduced from evacuating the crankcase.
Even the Ford Flathead guys are using PCV's these days.
Mike G
