replacing downpipes

[clayt74]

Hi all,
Ive got to try and replace my original downpipes at the weekend for some nice shiny motad ones, i have been spraying the header bolts with plus gas all week to hopefully ease the chances of stripping or snapping studs

anyway my question is; is it necessary or advisable to remove the radiator before trying to remove the downpipes??
or should it be simple enough just using extension bars?

any advice greatfully recieved.

Cheers