Well since I’m biased because so far it all worked the short answer is I recommend every single article and book he wrote haha but if someone said that to me I’d have been like the hell am I reading that much. But over time, I did read all of it anyway.
In all seriousness, since you were very phisiqe focused, I’ll make a bit of an assumption that you like pump and muscle focused work, but I may be wrong. If I’m right, then what I would say is pick a template that allows for a bit more assistance work, instead of the big movements only, although all his templates call for squat, bench, deadlift and military press as main moves, some adding the power clean in as well. However, some have a focus on less work on the main lifts and more room for assistance which would make the transition smoother.
On the other hand if you enjoy variation and new things, dive into a template that’s more focused on main lifts and leaves room for only necessary assistance work, like leg raises, face pulls, chin ups and rows.
One template that’s good to start with if you have the time of 4 days a week is the Triumvirate, its available on T-Nation for free as an article, think it’s called something like ‘How to build pure strength 531’ also explains the basic concept of Wendler’s principles of program design.
The only thing is, he doesn’t go far into conditioning in that article but in his later books it becomes one of the pillars of the program, mixing light conditioning like weight vest walking with hard conditioning like prowler and hill sprints, and daily mobility work like Agile 8.
If you are interested in more, I’d very much recommend his newest book 531 Forever, but previous ones like Beyond 531 and the first book he wrote about the program are also useful and worth buying if you are curious, although you will find you know most things already if you read his articles and buy Forever. He has tons of free templates he wrote on T-Nation and his own website as well, like 531 Beach Body, Building the Monolith, Boring but Big, Rest-Pause challenge, Beyond 531 template, Krypteia Redux, just to name a few.
All brilliant and effective programs but I would say start with Triumvirate to get a feeling of the program, maybe with some added prowler work once a week for starters and not too heavy first, and read the full article of it, that way it will be easier to understand his evolved concepts like Beyond or the Templates in Forever.
Well this got a bit long but I hope you can find something helpful in it
Edit: forgot to mention, in regards to your phisique, as long as you keep improving the main lifts and push the assistance work hard but smart so they don’t end up taking away from the main work, you will still maintain if not actually improve your phisique, provided you eat enough protein, and enough calories to recover from the workload