I replaced , timing chain and gears, on a late 70's 460, in a class C. Next engine component behind the water pump.
Didn't have the bumper off, probably 1/2 hour re & re, but nothing I did would have been accessible with just the dog house off.
JMHO: The guys that say it can be done from the dog house, will be eating their words and wanting to change their labor quote.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.