The compound & manor housing the secret weapons lab is the same location used in Magnum, PI as the Robin Masters Estate, The Robin's Nest. Comments by characters in the Magnum, PI series reference 5-O and McGarrett implying these two shows are in the same multiverse.
Last show of the series.
The assault rifle used by Wo Fat and the Red Chinese (Valmet M76) is a derivative of the Soviet Kalashinkov (AK47 and its variants).