Use the same nickel-alloy stick welding rod that's used to repair cast iron to run a penetration pass on the spring perches. Reverse-polarity DC current is the best approach for getting a smooth bead with good penetration. Once that bead is well-bonded to the cast steel, use 7014 or 7018 reverse polarity DC rod to build up cap passes and bond well to the steel axle tubes. Post-heating or slow cooling should not be necessary, but you might want to spend 10 minutes or so after each pass stress-relieving the weld bead by peening all over with the pointy end of a slag hammer. Bury the housing in sand overnight if you're worried about the rate of cooling.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!