'72 C10, great truck! We can make some inferences here on what you're looking to accomplish with that advertised duration. But, in order to give you anything better than a guess, we need more information. Ideally you would get the "best" cylinder heads, within your budget, for your application and then select a camshaft accordingly. As a rule, finding a camshaft to fit the cylinder heads is a much easier task than finding cylinder heads to fit a camshaft. In this case you're going to be just fine. It's just a heads up for the next project.
Any information you can provide about the rest of the build would be helpful. What size engine and what pistons? Automatic or manual? Rear end gear ratio? How is this truck going to be used? What is your budget? Is this a fresh build or how many miles on it?
This is just a jumping off point. When some of the folks here that really know their stuff chime in...the more information you can provide the better the recommendation.
In general need to know more about the engine itself. There are some tricks that are buried inside aluminum head’s so knowing what engine and what things have been done to it as in pistons being used whether the block was decked or not are useful tidebits of information.
These lead into understanding if your desires for aluminum head’s and the rest of the components work together well or not so much which leads into your expectations of power and of course how much budget is available, aluminum head’s run from 200 dollar bare but machined Chinese imports to 5,000 dollar ready to run domestics so your finances are our guide to big extent as they are with the contributors here. The lower cost base heads require you obtain tge missing parts the good side is these castings are usually pretty decent so you can outfit them with higher end parts for some decent performance for less overall cost but you need to have some head assembly tools with a bit of mechanical ability to get them together.
So we need some deeper degree of information to be of help.
265 Advertised? Probably similar the 268HE CompCams I have. I would go with the 200 cc type with the 64cc Chambers. With .041 Head Gasket you should be around 9.0:1 CR and no problem with Aluminum heads. I am running Vortecs with the 268 HE. Right at 10.0 CR, Dynamic is 8.0. If you have a cam card it will tell you when your ABDC Intake valve closer point is. Yours is going to be around 58-60 degrees like mine if that is advertise duration. Go to Wallaceracing.com . Look up Engine calculators.