1979 Malibu 305 cu in with a small coolent leak at intake manifold by the
no. 2 plug. what is wrong and what to do?

Is coolant entering oil ? If so, replace manifold gaskets.
Sometimes, the bolt itself leaks " a little " and coolant appears, but
stays outside of oil system. Weeping bolts can be fixed with a few
twists of yarn, and a re torquing. The yarn compresses, sealing the bolt.

The thermostat gasket might leak a bit, resulting in water at front
of manifold. UV dye test ?

The intake on a SBC isn't * that * hard to do, here's some tips;
Crank engine to # 1 TDC on firing stroke [ rotor points to # 1
terminal, timing marks align ] put a paint mark on firewall to simplify
dist. re-installation. After tear down and cleanup, glue oil seals down
to block. I like permatex # 2 [ slow drying ] or contact cement [ fast
drying.] Lightly glue manifold gaskets to block. When glue is dry,
give oil seals heavy coat of Permatex # 2 or silicone if your in a
hurry. Put a light coat of sealer around water passages, front and rear.
Promptly place manifold over fresh sealer, install end bolts first, in
pairs, torque to approx. 10 ft lbs, and install rest of bolts, the trick
is to get the water passages to seal, than torque down manifold using
factory torque specs, and sequence. Align distributor to paint mark on
firewall, let sealer dry throughly, and set timing after engine fires
up. Be sure distributor fully seats, if not, oil pump may not be driven.
Sometimes, oil pump turns a bit when distributor is removed, use a huge
screwdriver to turn pump shaft to align with oil pump drive slot in base
of distributor gear.

Could be coolant following bolt threads [ nuisance leak ] or a failing
intake manifold gasket, which would allow coolant to enter oil system.
Wash down engine, and check around thermostat housing. Replacing
manifold gaskets isn't * that * bad, but some tips apply.

Crank engine to # 1 TDC, and ensure rotor points to # 1 distributor
terminal and timing marks align. Make paint mark on distributor body,
manifold, and firewall, these marks will simplify distributor
re-installation. If rotor points to # 8 rotate engine one turn
before removing distributor. After tear down and cleanup, glue oil
seals to block using contact cement, gasket sealer stays slick too long,
you want the seals to stick tight to block. Put thin coat of sealer around
front and rear water ports on ends of block, put heavy coat of sealer
over glued down oil seals. Put thin layer of sealer around water ports
on manifold, and promptly install manifold to fresh sealer, install, in
pairs, bolts around water outlets, and torque to 10 Ft Lbs. Now install
remaining bolts, and torque in sequence to spec [ 18 Ft lbs ? ]

Align distributor rotor to painted marks, and be sure oil pump tang
is engaged, distributor drops down flush, if distributor rides high,
remove, and gently rotate oil pump shaft with huge screwdriver, and try
again, don't expect rotation of engine to align tang and shaft.

Let sealer fully cure before filling with coolant. After engine
fires up, reset timing.