Need a NEW heater core for a 1998 Monaco Windsor Part number I have is E56407. I found one place at $276 surely there is another source for less than that---if not I'll just bite the bullet.
Went to work on this thing about 9AM and 6 hours later it was all done. There is some questionable stuff about the original installation but I got through it all and it works. So a total of 11 hours and $200 for the heater core so even at 80 years old you can take on a project like this.