<VV> Exhaust port tube fit to manifold

[Doug Mackintosh]

I have to replace some the exhaust port tubes in the heads of the engine I am working on, because the donut seats are torn. I have some used tubes. 
According to the 1961 shop manual the tube ends are a press fit into the exhaust manifold (as well as into the head). The used tubes I have are a sloppy fit in the head (missing a press fit by as much as 0.031 inch). 
 
Any experience on the list with this. Should I use these, or do I have to bite the bullet and purchase more used ones? I am guessing the press fit would help with heat transfer from the tube to the exhaust manifold, but as a practical matter, does anyone know what will actually happen if the fit is sloppy?
 
Thanks!

-- Doug Mackintosh
Corsa member since 1996
Corsa/NC member since 1996, Virtual Vairs member
Corvair owner 1969-1971 and 1996-on