hei type distributor 73 340 duster

i am thinking of going to a hei type distrbutor setup in my 73 340 duster, i am seeing that you eliminate the coil , ballast resistor , and ecu box. first is this a smart move? second MSD units are on the high $$ side . i see proform has unit for around $235. can use the plug wires i have now? they do work fine, also would i need a spark box like MSD street fire unit? i have heard the proform unit 67040 which is what i am looking at is larger then the stock unit i am using now. car is not being raced at all, just seeing if anyone else is using this set up and if they like it, thanks for any info. forgot to ask not sure if this unit will have clearance problems with fire wall and so on. the MSD units cap looks more like the stock size