Warning: When installing an updated duel chambered master cylinder under the floor of an older GM truck, a brake line modification may be necessary.
It is not acceptable to allow the modified brake line to touch or be very close to the exhaust pipe. During long trips, the exhaust heat can cause a rise in the brake fluid temperature to near boiling level. Modern master cylinders do not have a vented cap to release line pressure so fluid will be forced out through wheel cylinders. The early single chambered caps are vented to prevent this.
Check your brake lines on non-original trucks. Do not allow a safer system to leave you without brakes.