'68 engine assembly is about as straightforward as you can get - with the exception of the windage tray, it assembles just like any other early small block when utilizing the correct parts. Speaking of parts, you can use esteemed CGR members Alan Colvin's book Chevrolet by the Numbers, and Jerry MacNeish's 1967-68 Defiinitive Facts books and gorge yourself on part numbers. Carb to pan, intake to exhaust, everything you need to source and search for are spelled out in good fashion. Part numbers and visual references abound.
No, I'm not a publisher, nor do I get royalties from either, but I have read and reread these and others until I fell I have a pretty good grasp of what's needed to put one together as original. I have built SB Chevys since age 16 (44 years), and so I did my latest, '68 MO, waiting to be painted, topped off and installed. Top to bottom, you can still put one of these together, correctly, on a budget.