Will a 350cu in 1979 Camaro slide into 1978 trans am?

No, a 350 cubic inch engine from a 1979 Camaro will not simply "slide into" a 1978 Trans Am. While both cars commonly used the small-block Chevy 350, there are significant differences in the engine bays and associated mounting points. Even if the engine itself is physically close in size, the accessories (alternator, power steering pump, etc.), exhaust manifolds, and engine mounts are likely to be incompatible. You'd need significant modification to make it fit.