How thick? Guide sizes can be manipulated, although it gets to be pricey.
D16=>5.5mm
Subaru=>8.0mm I only have listings of 76 to 05 and not all of the EJ family.
VOLKSWAGON 86-92 2109CCINTAKE P3467 1.57 X 8MM X 4.81 X 3G <--- too many grooves and too big of valves
EXHAUST P3466 1.33 X 9MM X 4.83 X 3G <--- too many grooves and too big of valves
PONTIAC 77-80 151 CC (ironduke w/ non- crossflow heads)
IN 79-80 P3063 1.72 X 11/32 X 4.66 X 2G <--- too many grooves and too big of valves but usually super cheap.
EX 79-80 P3367 1.50 X 11/32 X 4.62 X 2G <--- too many grooves and too big of valves but usually super cheap.
OLDSMOBILE 75-82 260 C.I.
EXHAUST P2946 1.30 X 11/32 X 4.68 X 1G <-- a little too big
OLDSMOBILE 80-90 307 C.I. INTAKE P3205 1.75 X 11/32 X 4.66 X 1G
EXHAUST P2993 1.50 X 11/32 X 4.68 X 1G
There is a lot Olds engines that have the right length valves and single groove on the stems.
The stem dia. are around 8 to 9mm and have 1.5" to 2.0" heads.
Which would not fit very well in 4-valve D-series heads.
NISSAN 82-83 1488CC INTAKE P3279 1.45 X 7MM X 4.67 X 1G <-- Possibly a good candidate if you modify valve guides
EXHAUST P3278 1.18 X 7MM X 4.64 X 1G <-- Possibly a good candidate if you modify valve guides
NISSAN 83-84 1488CC TurboINTAKE P3280 1.45 X 7MM X 4.70 X 1G <-- Possibly a good candidate if you modify valve guides
EXHAUST P3297 1.22 X 7MM X 4.71 X 1G <-- Possibly a good candidate if you modify valve guides
MAZDA 94-04 2994 CC Ford Built INTAKE 94-99 P3485 1.66 X 8MM X 4.610 X 3G <-- a little short and the head are a bit big.
INTAKE 00-04 PV4598 1.66 X 7MM X 4.630 X 3G <-- a little short and the head are a bit big.
EXHAUST 00-04 PV4599 1.37 X 7MM X 4.610 X 3G <-- a little tall and the head are a bit big.
EXHAUST 94-99 P3484 1.37 X 8MM X 4.610 X 3G <-- a little tall and the head are a bit big.
GM 85-88 1.0 L Sprint
INTAKE P3808 1.41 X 7MM X 4.55 X 1G <-- a little short and the head are a bit big.
EXHAUST P3807 1.18 X 7MM X 4.51 X 1G <-- a little tall but a possible candidate
GM 83-86 2.0L Brazillian built (Opel) INTAKE P3175 1.60 X 8MM X 4.70 X 1G<-- Possibly a good candidate if you modify valve guides
EXHAUST P3174 1.37 X 8MM X 4.72 X 1G<-- Possibly a good candidate if you modify valve guides
I have no spring install height ATM but I can dig up some later. ;D