http://www.flickr.com/photos/josengsisiw/5039051614/

They could swap in front end parts from Japan surplus Hi Ace or even from chop-chop.
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I'm not sure how you assume that the Urvan Escapade cost more to maintain? It is used by many in the transportation business much like the L300 Versa Van and as well as other business segments.
Presently, the Philippines market does not have any ambulance that meet your criteria. Tried riding on a HiAce Super Grandia? Its not comfortable at all and it costs almost equivalent to two Urvan Escapades. Its engine is a 2.5 li that is also found in the Innova. If a fully loaded Innova feels lethargic, what's more a fully equipped ambulance?