if the engineering shop of your choicing is any good they will make the harded seats for you, i do,
a point of interest for you all, i have owned hillmans for many years and as such know the hillman engine well, the ali head will last 6 thousand miles before valve seat recession, with a good addative that will extend to 15 thousand, the lead that is found in leaded fuel is what protects and lubicats the seats and valves, so for this engine i usally after 3 full tanks of unleaded i put in 1 tank of the leaded fuel in, my hillman hunter 1725 has been like this for the last 9 years and 45 thousand miles, the superminx has a cast iron head is done the same way and has been like this for 4 years and 12 thousand miles. both head gaskets were done last year (because i was bored) and i can report there has been no valve recesion.
this dose depend on how you drive, if you push your car/van/camper hard, the valves hit the seat harder as so suffer more, if you drive with care, do not let the engine labour etc etc you will have no problem for many a mile
if you tow a lot though get the head done.
as a rough price guide and providing you take of the head do not expect to pay more than 150 pounds to have the head converted, if you cannot take of the head and they do it for you you could pay about 300 pounds, but with the latter it will be difficult checking there work and you might have problems later.
hope this helps ian
1963 Hilman super minx
1978 Austin Maxi x2
1963 Moggy Minor
and a land rover disco
and
1 wife
6 kids
2 dogs
1 cat
lots of debts
am I happy oh crap YES
coming soon to a screen near you the restoration of YGV 775S