Welcome to the forum
A big block is fairly easy to do. It somewhat depends on which trans you plan to use. An auto is easiest. If that is what you want, I would recommend either a TH400 or 4L80E with the latter being my preference. With a manual, it is easiest to convert to a hydraulic clutch. There are several trucks here on the forum with big blocks and just about everyone has their own idea on how to make it work. There is also a thread or two on just big block swaps. Check out member 60-66's latest '63 project with a big block. It is titled 'Finished my 1963 SWB'.