1981 C3's are very special cars. They are the only corvettes to be built in 2 factories at the same time. They were the first to be fitted with computer command control as standard and had a unique engine, the L81 that was certified for all states in America. Both auto and manual could be ordered. A new fibreglass mono-leaf rear spring was fitted to all cars with auto boxes and standard suspension. However, they were generally considered gutless because of emission regs and catalitic converters. So after 40 years of use you will lift the bonnet of any '81 and find they are all different/modified. Look at one photo and it may look familiar to yours but chances are it 'aint! Most owners ditched the CCM system and bought aftermarket upgrades (there are loads to choose from). Oddly, mine has retained the original CCM but has undergone a radical transformation with hotter cam, roller rockers, HEI distributor, Bowtie 4 speed gearbox, trans cooler etc. etc. My point is, no 2 cars are the same even if they were born the same (unless they are still bog standard in which case, gutless).
Your recently acquired C3 has been modified but to what extent is uncertain? Hopefully, the car came with some history and receipts so you will have an idea. The fun of owning a C3 (as with any classic car) is learning how it's been put together. As 'Dazza' said, get a workshop manual - you will probably need it! Glad to see you have joined the CCCUK (welcome) - a good source of info and help.
I notice from your engine photos that the bonnet opening cables look worn? The first job on your list should be to change them and/or install secondary pull cables that can be accessed from the underside of the wings. If one snaps the bonnet will not open - definitely not worth the hassle!
Good luck and look forward to meeting you at a Sussex meeting one day soon.