First of all Welcome to the site.
You say you changed the oil to Castrol 10-30, you may want to look into past threads on oil because not any oil off the shelf is good for these solid lifter/flat tappet engines. they have done a lot to oils lately to protect the life of catalytic converters by taking out the anti scuff additives ZZDP Phosphorus, zinc etc. Most people are using Shell Rotella 15-50 or equivalent heavy duty deisel oil or a Racing oil which still has the good stuff for these old engines.
Ted may be able to lead you to some past threads on this.

55 Vicky & customline
58 Rack Dump, 55 F350 yard truck, 57 F100
59 & 61 P 400's, 58 F100 custom cab, 69 F100, 79 F150, 82 F600 ramp truck, 90 mustang conv 7 up, 94 Mustang, Should I continue?