I've got a '93 E2000 (ex courier van 749000 km and counting) and I know guys that have a 302 and a supercharged v6 from a commodore into theirs....As the saying goes there is no replacement for displacement get an engine from a E2000/2200/2400 they are all petrol and should bolt straight in or use the 2600 from the Bravo/Courier. Alternately go to an import wrecker and see what the Bongo van from the similar year has as they are usually low km and turbocharged
If memory serves me right the E series vans from 86-95 are essentially the same mechanically