i have to replace the heat exchanger on my old Volvo MD 17C engine. Instead of paying $1600.00 for the OEM, i had one made for $350.00. I now have to mount it remotely and use heater hose instead the the preformed Volvo copper tube. I should have done this years ago for various reasons. The brass ports on the new heat exchanger are yellow brass 1/2" FNPT ports. I need 1/2" MNPT to 5/8 barb. I priced these at the local independent auto parts store for about $9.xx/fitting. Also need some 45s etc same price. I notice online, i can get them for $2.39/fitting. All "brass". Are there different qualities of brass? I cannot get the meterallugical breakdown of either...anybody else run into a similar dilemma? Should I pony up?