The 1986-1990 FSM lists no torque specs for the rear mounts or lower front mounts.
There is only one spec in the 79-85 FSM (rear motor mounting bolt-nut: 16 to 24 ft lbs) and the 86-90 rear mount is the same part from 84-90.
For the rest, there are general “Torque Value” charts in the front of the service manual. ¹⁾
It lists general torque values for bolt types but not specific mounting bolts.
It also says to torque to these values given in the tables unless specified otherwise. There are two charts (English and Metric).

Below is a list of torque values from the different year model FSMs.

Torque Specs in HD Service Manuals
1986-1990 Engines
Upper Front Mount to Head	25-30 ft-lbs 2)	34-40 Nm	Upper Front Mount to Frame	30-35 ft-lbs 3)	40-47 Nm
Top Front Mount to Heads	25-30 ft-lbs 4)	34-40 Nm	Top Front Mount to Frame	30-35 ft-lbs 5)	40-47 Nm

The charts below are from the torque value charts in the 86-90 FSM.
⁶⁾

SAE Torque Value Chart per Bolt Type
Bolt size	SAE 2 74,000 psi Low carbon	SAE 5 120,000 psi Medium carbon heat treat	SAE 7 133,000 psi Medium carbon alloy	SAE 8 150,000 psi Medium carbon alloy	Socket head cap screw 160,000 psi High carbon quenched tempered	Socket head set screw 212,000 psi High carbon quenched tempered	Studs
#6	-	-	-	-	-	9 in/lb	Use SAE 2,5 and 8 values when grade is known with nut and sufficient strength
#8	-	14 in/lb	-	-	-	16 in/lb
#10	-	22 in/lb	-	-	-	30 in/lb
1/4“	6 ft/lb	10 ft/lb	13 ft/lb	14 ft/lb	16 ft/lb	70 in/lb
5/16”	12 ft/lb	19 ft/lb	25 ft/lb	29 ft/lb	33 ft/lb	140 in/lb
3/8“	20 ft/lb	33 ft/lb	44 ft/lb	47 ft/lb	54 ft/lb	18 ft/lb
7/16”	32 ft/lb	54 ft/lb	71 ft/lb	78 ft/lb	84 ft/lb	29 ft/lb
1/2“	47 ft/lb	78 ft/lb	110 ft/lb	119 ft/lb	125 ft/lb	43 ft/lb
9/16”	69 ft/lb	114 ft/lb	154 ft/lb	169 ft/lb	180 ft/lb	63 ft/lb
5/8“	96 ft/lb	154 ft/lb	215 ft/lb	230 ft/lb	250 ft/lb	100 ft/lb
3/4”	155 ft/lb	257 ft/lb	360 ft/lb	380 ft/lb	400 ft/lb	146 ft/lb
7/8“	206 ft/lb	382 ft/lb	570 ft/lb	600 ft/lb	640 ft/lb	-
1”	310 ft/lb	587 ft/lb	840 ft/lb	700 ft/lb	970 ft/lb	-