Join Date: Sep 2000
Location: Shrewsbury, MA, USA
Yes it will fit but it will require removal of the inner heater box, new heater core, and most likely removal of the passenger side fender to get the old small block heater duct off the firewall and a new big block one installed. The heater tubes on a big block come out of the heater duct near the hood hinge, and it is a different part number from a small block heater duct.
GM lists two different part numbers for the inner heater box, one number for a big block and one number for the small block in the Assembly Manual (AM). Don't know if this is because the part, as shown in the AM, is an assembly with the appropriate heater core already in it, or if there is actually a difference in the box itself.
If you want to do it cheaply, just buy a big block heater core, mark on the engine side ductwork where the heater tubes will go and drill 2 one inch holes through your existing duct. Then just plug up the holes left at the edge of the duct where the small block heater tubes came thru with something. Seal around the heater tubes with some firewall seal and stich your hoses back on.
1969 Indy Pace Car
350/300HP RPO Z11
[This message has been edited by Mark C (edited 02-01-2001).]