Crazy-Crazy!
You have a >25 year old piece of equipment that if recapped with high quality capacitors for a relatively modest cost will probably be good for another 25 years, and if not should still be repairable.
You want to put in modern SMPSUs that will probably only last five years, unless you buy really expensive western branded ones with extended warranty, then you may get ten or fifteen years out of them. This will cost a *LOT* of money and if the equipment uses low level analog signals the circuits may not have enough PSRR to handle the resulting HF ripple on the supply rails and still stay in spec. Also, when they do die, there's a significant risk* of them severely over-voltaging the supply rails blowing the s--t out of all the ICs on the board and rendering it B.E.R.
*Greater IMHO than the risk of a well designed and constructed linear regulator run within its ratings failing shorted and doing the same, because there are more possible points of failure.