Hi Tim, you can think whatever you want. If you're an engineer, then do the numbers! OK let's assume a one inch cube of iron connecting the two. (you can change that to whatever you want.) I calculate that it will have a thermal of resistance ~ 0.5 K/W (assuming iron thermal conductivity is 80 W/(m*K) ) For the proposed 100 K temperature difference that's 200 watts.
And this doesn't include the contact resistance.. which I've found to always be bigger than you'd think too.
Sorry I've been doing a lot of heat transfer calc's lately, conduction, convection, radiation...
George H.