1953 239 flat head

[dynamikechris]

I am a new owner of a 53 F100 from British Columbia. It’s a stock 239” flat head.Time to do an oil and filter change. What type of oil do guys recommend? I’ve been told to use 15/40 Diesel engine oil. What’s your thoughts. It is only a fair weather driver and stored in a heated dry shop so winter driving won’t be an issue. Any advice and information will be appreciated! Thx!