The 760 had either a turbo 4 (most highly regarded of the options),
a PRV v6 which is reputed to be not bad towards the end of its
lifecycle, or a turbodiesel VW derived I6 motor that is well regarded
among VW people but not well regarded among volvo people. Both the
V6 and the I6 are quite sensitive to oil but otherwise are average
modern motors while the turbo 4 is a direct relation to other
redblock volvo motors are are quite amazingly sturdy.


As far as putting another motor in to get more go, I'd go for a
ford or chevy V8 instead of another volvo motor. If I wanted just
another volvo motor, I'd probably just sell the car and buy another.
The turbo 4 can make huge amounts of power and you may be able to
get someone who races diesel VWs to hot up the turbodiesel, but
in either case you'r far better off just starting with a factory
car.
chris