1995 Ford F-350 Van hard to start when cold

1995 Ford F-350 Van mileage: 122,000. I am having trouble with cold starts on this work vehicle. When cranking to start, sounds as if engine is not getting fuel, but it usually starts after prolonged cranking and pumping of accelerator. We have had fuel pump changed, injectors, fuel filter, cold start solenoid, and there has been little improvement. As a result, starter and battery are taking a beating from all the extra starting work. This problem seems to be directly related to the temperature in our shop. We have heat in the garage, but it only keeps the place about fifty degrees or so. When we get cold weather (ten to fifteen degrees) the problem gets worse. Would a crankcase heater help this problem? I know larger diesel trucks have plug-in warmers for winter use. Is this something we should look into? How difficult is it to install? Appreciate any ideas you can offer.