can anyone tell me what generation the 1988 454 365hpMags are. and can anyone tell me about the internals, how they are built. pistons cast/ forged? rods? heads?

Glass Dave,
Your 1988 454, 365 hp magnums are a Mark IV series engine.. This as opposed to Gen 5 or Gen 6...
The engine(s) are forged pistons and crankshaft. Rectangular port heads, likely the last 3 digits of the cast numbers are 990.
Flat tappet cam. I believe the rods are the dimple rods. These engines are pretty beefy.

thanks QD. i just picked up a 34 Scarab III with these engines in them. i got it on a trade and am going to sell it. some perspective buyers have asked me about the engines and i was not real familiar with them. they have 450 hrs on them(not hard either). would that be considered alot? if these were freshened up and brought up to the 450-500 HP range, is the rotating assembly and related components up to the task?

we brought a couple 88 454s mags up to about 475 and they ran great no probs

If I didnt just have to buy a car, Id be all over that Scarab. The engines are very upgradable. Cams, Jimv shims in the heads and a decent exhaust and they are good for 450-500. They will handle blowers without much effort too. Bottom ends are all steel forged.